Linux process command help (part 2)

Hi, for each command I need to explain what the command does and then show some of the output

For example:

ps << this command shows the running process

PID TTY TIME CMD

1250 pts/5 00:00:00 bash

1500 pts/5 00:00:00 ps.

The commands that I need solved are:

$ ps -f -u userid

$ ps aux --sort=-pcpu,+pmem

$ ps aux --sort=-pcpu | head -5

$ ps -f --forest

(I'll be posting the other questions as seperate parts)