What is Datastore?

The data store provides a repository of persistent information about the farm that each server can reference, including the following:
• Applications
• Administrators
• Folders
• Installation Manager groups
• Installation Manager packages
• Load evaluators
• Printers
• Printer drivers
• Policies
• Resource Manager metrics
• Servers
• Isolation Environments
• Farm configuration information
• Published application configurations
• Server configurations
• Trust relationships

Database

For Citrix Presentation Server we can find three types of Databases.
Data Store
Data Collector
LHC (Local Host Cache)

Requirement for Citrix server installation:

System Software Requirements:

We can install MetaFrame Presentation Server on computers running the following Microsoft operating systems:
• Windows 2000 Server Family: Windows 2000 Server, Windows 2000
Advanced Server, and Windows 2000 Datacenter Server; Service Pack 4 or later
• Windows Server 2003 Family: Windows Server 2003, Standard Edition,
Enterprise Edition, and Datacenter Edition
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Important ~ You must install the Terminal Services component before you install MetaFrame Presentation Server. Terminal Services is not installed with Windows by default; you can install it with Add/Remove Programs in the Control Panel. Install Terminal Services in Application Server mode.
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System Hardware Requirements

The following requirements are based the operating systems on which you run MetaFrame Presentation Server:
Windows 2000 Server and Advanced Server - Microsoft recommends a 166MHz or
faster Pentium-compatible processor, 256MB of RAM, and a 2GB hard drive with
at least 1GB of free space.
Windows 2000 Datacenter Server - Microsoft recommends an eight-way or greater
array of Pentium III Xeon processors, 256MB of RAM, and a 2GB hard drive with
at least 1GB of free space.
Windows Server 2003, Standard Edition - Microsoft recommends a 550MHz or faster
Pentium-compatible processor, 256MB of RAM, and a 2GB hard drive with at least
1.5GB of free space.
Windows Server 2003, Enterprise Edition - Microsoft recommends a 733MHz or
faster Pentium-compatible processor, 256MB of RAM, and a 2GB hard drive with
at least 1.5GB of free space.
Windows Server 2003, Datacenter Edition - Microsoft recommends a 733MHz or
faster Pentium-compatible processor, 1GB of RAM, and a 2GB hard drive with at
least 1.5GB of free space.

All servers running MetaFrame Presentation Server must have graphics capabilities
of a minimum of VGA 640 x 480 pixels.
Set the displays for computers running the Presentation Server Console to a least
800 x 600 pixels.

What is Citrix?

Citrix MetaFrame Presentation Server is a technology that can allow remote users to connect to applications that are actually installed on a remote computer. It uses a mix of technology that results in that remote application looking and behaving just as though it was installed on the local machine.For example, if an application needs to be made available to a group of users who are off campus, the application can be installed on a Citrix server and access will be given to the users who need to use it. Those users can then go to a certain web address, log in with their credentials and click on an icon on that page for that application. It will then appear as though the remote application will start and run on their remote computer, when the application is actually being executed on the Citrix server and screenshots and mouse/keyboard inputs are being sent back and forth between server and client. They would be "remote controlling" the application running on the server from their computer so the application need not be installed on the local machine. The remote application can be minimized / maximized / resized just like any other local application. Using drive mapping, files can be also be opened on and saved to the local computer that the user connected from.