The fg command allows us to continue a stopped operation by running it in foreground.
The command name stands for foreground.

Usage

The default fg command syntax is: 
fg [%job_number]
The parameter [%job_id] contains the job number you wish to run in foreground. If this is not indicated, the command will run the last stopped operation.

Stop a working job

To stop the execution of a command so that it can be later resumed with fg you need to press the ctrl + Z keys. The job number to be used with the fg command will be printed. 
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^Z
[1]  + NNNN suspended  top