# Principles of Operation of Different Types of Robots in the Orchestrator
## **Operation Principle of Attended Robots in the Orchestrator**
**Attended robots** are Robots that are launched on the User's computer in the following ways:
* manually by the User;
* from startup;
* via a keyboard shortcut;
* according to a local schedule.
The “Sherpa Attended Robot” licenses are personal. One license is launched from one User account and is licensed only for that account.
Attended robots can be added to the Orchestrator, but this type of Robot will not be launched from the Orchestrator by creating Jobs on the “Jobs” screen or scheduling on the “Triggers” screen. That is, Attended robot scenarios are launched only locally.
Attended robots have a limited list of capabilities in the Orchestrator.
For example, it is advisable to register an Attended robot in the Orchestrator in cases where it needs to be used in verification station mode for an Unattended robot that processes documents or applications in a batch mode. The Unattended robot processes all requests that do not require human interaction, while the Attended robot in verification station mode can be used in the application processing at any stage when it is necessary to involve a person to make a specific decision (that is, to verify manually). Such an Attended robot (verifier) accesses the Queue and takes from it a Task that was placed for it by the Unattended robot.
Attended robots have access to Queues created on the “Queues” screen; they can also receive Tasks from Queues, take these Tasks for processing, and change their status.
## **Operation Principle of Unattended Robots in the Orchestrator**
**Unattended robots** are Robots that are launched without human involvement and are managed only through the Orchestrator. Unattended robots are launched:
* according to a schedule created on the “Triggers” screen;
* through Task Queues created on the “Queues” screen;
* via API.
Sherpa Unattended-Robot licenses are competitive. One license allows the execution of a scenario under the management of the Orchestrator on the account of any user (including a virtual account created specifically for the robot). The total number of licenses used at any one time cannot exceed the number of licenses registered in the Orchestrator.
An Unattended robot can be used:
* with manual user session launch. That is, if the Orchestrator sees that the Robot is online (green indicator), then the Orchestrator can assign it a Job. In this case, the Robot's account must be launched manually;
* with automatic user session launch;
* in a classic scheme when there is an RDP server.
## **Operation Principle of the Unattended Robot Coordinator**
**Coordinator** is a service that must be installed under the Administrator account of the RDP server (terminal server) on which Unattended robots are planned to be launched in user accounts, provided that automatic login to Robot accounts is required. The Coordinator serves to launch local User sessions along with Unattended robots on terminal servers running Windows operating systems.
There is one or more accounts registered for Robots on the server. The server itself runs continuously, but the accounts do not work by default. Accordingly, if the Orchestrator has assigned a Task to a bundled Robot, it must activate that Robot, and for this, it must activate the corresponding account on the server. This is the purpose of a special component – the Coordinator.
The Coordinator is a separate program that does not require a license, is installed under the Administrator account of the RDP server, and runs as a service.
**The task of the Coordinator:** upon command from the Orchestrator, to establish and maintain an RDP connection to a local or remote user account, in which the Unattended robot is then launched.
For Attended robots, specifying the Coordinator is not required.
The Coordinator is installed from the corresponding distribution. [The installation of Sherpa Coordinator is described here.](https://docs.sherparpa.ru/en/sherpa-rpa/sherpa-orchestrator/razvertyvanie-platformy-pod-upravleniem-orkestratora/ustanovka-sherpa-rpa-coordinator/ustanovka-sherpa-rpa-coordinator-na-windows) The Coordinator does not require a separate license.
A Robot with Coordinator functionality (for Unattended robots) is displayed in the Robots table. The Coordinator is always in an active state, indicated by a green indicator. This service ensures the creation and maintenance of user account sessions for Unattended robots within the used terminal server.
All other Robots are technical accounts running on the same terminal server.
If your configuration includes a terminal server (Windows Server with RDS roles and licenses), please note that the Coordinator must be installed with administrator rights. And SherpaRPA Runtime should be configured in Unattended mode for each user account on this terminal server so that they function as Unattended robots.
In case you do not have terminal servers, but only a grouping of virtual machines, one of them should be allocated for the Coordinator. This virtual machine must be constantly powered on, as it will ensure the operation of Unattended robots on other machines. At the same time, on the virtual machine itself, according to the standard Windows RDP license, you will be able to install one Unattended robot in a user account.
The Orchestrator assigns the task to the Coordinator of the corresponding terminal server to create an RDP connection to the local or remote account allocated for the Unattended robot:
* according to a schedule,
* via API call,
* by Robot command,
* by another supported Trigger.
At the same time, multiple such accounts can be hosted and actively used on one terminal server. Access to the Unattended robot account is performed with the login and password provided to the Orchestrator.
On the Orchestrator side, this process looks as follows:
1. After creating a Job, the Orchestrator determines that the Unattended robot is unavailable and has been assigned a Coordinator that is available, as indicated by a green indicator.
2. The Orchestrator sends a command to the Coordinator to enable the account of this Unattended robot.
3. The Coordinator receives the command and establishes an RDP connection with its own account on the server, where this Robot is located. That is, it launches the RDP connection, the account is enabled, and the Unattended robot is launched within the account. In the list of Robots, its indicator turns green.
4. The Unattended robot contacts the Orchestrator, and if there is a Task for it in the Jobs, it accepts it and processes it.
5. After completing the Task, the Robot will automatically log out of its account, and the account will be completely disabled.
If the Job is executed by the Robot from the Orchestrator, it is important to disable remote debugging. Otherwise, the Robot risks not logging out.
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