The IT Stuff

R2 expands CPU support to enable customers to run with up to 256 logical processors.
Hyper-V in Windows Server 2008 R2 can now access up to 32 logical CPUs on host computers—twice Hyper-V’s initial number of supported CPUs.
Reduced Power Consumption
Hyper-V™  new features, Live Migration  enable moves between physical targets happen in milliseconds, which means migration operations [...]

Windows PowerShell is a new command line shell and task-based scripting technology that provides information technology (IT) administrators comprehensive control and automation of system administration tasks, increasing administrator productivity.
Windows PowerShell includes numerous system administration utilities, consistent syntax and naming conventions, and improved navigation of common management data such as the registry, certificate store, or Windows [...]

Server Manager is a new feature that is included in Windows Server 2008, which is designed to guide information technology (IT) administrators through the process of

installing, configuring, and managing server roles and features that are part of the Windows Server 2008 release.
Server Manager is launched automatically after the administrator completes the tasks listed in Initial [...]

Types of Groups:
Security
Security groups are used to control access to resources. They can also be used as e-mail distribution lists.It allow you to manage user and computer access to shared resources. You can also control who receives group policy settings. This simplifies administration by allowing you to set permissions once on multiple computers, then to [...]

DHCP (Dynamic Host Configuration Protocol):

DHCP server  automatically configured all the IP configuration information for your client machine like DNS Servers addrese , Default Gateway,Wins Server, Domain Prefix etc
It minimize the administrative burden
It By using DHCP there is no chance to conflict ip address.
Support multiple scope like Unicast,multicast and superscope.
Using as a relay agent [...]