Process Snapshot

ps

Shows running processes and their IDs.

Use

ps show running processes of current user in current terminal
ps aux BSD-style, show all running processes (-a) with user column (-u) inside and outside terminals (-x)

Useful Flags

-f show full information
-F show fullest information
-u <user> show processes running from <user>
-g <group> show processes running from <group>
-T show processes running in current terminal

pstree

Shows running processes in tree format.

Use

pstree show running processes sorted by starting order
pstree -a show running processes sorted by starting order with more information