Simple commands for managing processes.

Show all of the processes on the system along with their PIDs. However, it differs in that it presents output in a tree structure that shows how processes are related to each other and in that it provides less detailed information about each process than does ps.
pstree

Lost processes with their pid
ps -A | less
ps -a | less

Kill a process with pid 8280
kill -SIGTERM 8280
or
kill -9 8280

The a option tells ps to list the processes of all users on the system rather than just those of the current user, The u option tells ps to provide detailed information about each process. The x option adds to the list processes that have no controlling terminal.
ps aux | less

The top chunk of information give system statistics, such as system load and the total number of tasks. You can easily see that there is 1 running process, and 55 processes are sleeping (aka idle/not using CPU resources). The bottom portion has the running processes and their usage statistics.
top

To see a tree view, where hierarchal relationships are illustrated, we can run the command with these options:
ps axjf