Send job to foreground.
Syntax fg [jobspec ...]
Resume jobspec in the foreground, and make it the current job.
fg takes a “jobspec” available from jobs, not a PID.
If jobspec is not present, the shell's notion of the current job is used.
The return value is that of the command placed into the foreground, or failure if run when job control is disabled or, when run with job control enabled, if jobspec does not specify a valid job or jobspec specifies a job that was started without job control.
fg is a bash built in command.
“A true friend stabs you in the front” - Oscar Wilde
bg - Send to background