The process table in Linux (such as in nearly every other operating system) is simply a data structure in the RAM of a computer. It holds information about the processes that are currently handled by the OS.
This information includes general information about each process
- process id
- process owner
- process priority
- environment variables for each process
- the parent process
- pointers to the executable machine code of a process.
A very important information in the process table is the state in that each process currently is. This information is essential for the OS, because it enables the so called multiprocessing, i.e. the possibility to virtually run several processes on only one processing unit (CPU).
The information whether a process is currently ACTIVE, SLEEPING, RUNNING, etc. is used by the OS in order to handle the execution of processes.
Furthermore there is statistical information such as when was the process RUNNING the last time in order to enable the schedulr of the OS to decide which process should be running next.
So in summary the process table is the central organizational element for the OS to handle all the started processes.
A short introduction can be found in this thread:
https://web.archive.org/web/20190817081256/http://www.linuxforums.org/forum/kernel/42062-use-process-table.html
And wikipedia also has nice information about processes:
http://en.wikipedia.org/wiki/Process_management_(computing)#Process_description_and_control
http://en.wikipedia.org/wiki/Process_table