Understand processes on your Mac
3 simple steps
Open Terminal.app from Applications/Utilities folder and type command:
ps -A > process.txt
This command will list all currently running processes on your Mac and save this information into process.txt file in your home directory.
See description of processes and links to more detailed information, share your know-how in comments
Don't like idea of uploading of your proceses file?
Only minimum information (unidentified proceses) without any personal information will be saved to improve process database. Still in rare situations there can be some personal data exposed together with process information (like username of particular service). If you want to be sure, check process.txt file in text editor before submitting.
If you totally don't like idea of uploading your Mac processes information, you can browse existing process database alphabetically.
What are these processes in Activity Monitor on my Mac?
"Thanks" to closeness of Apple, it is pretty hard to get full understanding about processes running on your Mac. Hopefully this site will help you understand Mac OS X better.
Should I optimize Mac by turning off unnecessary processes/services?
No. But if you still are interested in optimizing Mac by disabling essential Mac OS X processes, first check opinion from clever people.