While a program is running, it is called a process. A process is uniquely identified by PID - process id. To find out the information about all the processes, you can use the following commands: pstree, top, ps.
ps lists the processes of the system. Without any arguments, it lists only your processes. To see all of the processes by all users, run
The first column mentions the user id who has started the process.
To continuously monitor all processes, use "top" command. This command is usually used to monitor which processes are running, taking up most CPU or Memory.
To learn more about command use man command name. So, please go through manual using command
man ps man top