Question : ps aux

what information exactly does 'ps aux' give you?

Answer : ps aux

it gives you all of process information in the system.

a Displays information about all processes with terminals (ordinarily only the user's own processes are displayed).
u Displays user-oriented output. This includes the USER, PID, %CPU, %MEM, SZ, RSS, TTY, STAT, STIME, TIME, and COMMAND fields.
x Displays processes without a controlling terminal in addition to processes with a controlling terminal.

Without a option, 'ps ux' will report only the user's own processes.
Without u option, 'ps ax' will report all the process with PID, TTY, STAT, TIME, COMMAND fields only.
Without x option, 'ps au' will report only process with a controlloing terminal. For example, program A fork program B, then program B do not have a controlling terminal. All of daemon process do not have a controlling terminal.

I hope this help.