Hi,
I presume you mean %SystemRoot% in the first one. These are environment variables that are used by the operating system to determine various options.
To see a full list in operation, open a command prompt (start -> run CMD.EXE) and type SET | MORE
To answer your questions, however:
SystemRoot contains the top level directory of the Win2K installation. It is normally C:\WINNT
TEMP is the directory where the operating system should direct its temporary files to. This will vary depending upon the user logged into the system.
John