nohup is a POSIX command to ignore the HUP (hangup) signal. The HUP (hangup) signal is by convention the way a terminal warns depending processes of logout.
Output that would normally go to the terminal goes to a file called nohup.out if it has not already been redirected.
nohup is a low-level utility simply configuring a command to ignore a signal. As seen below, nohup is very far from being a full-featured batch system solving all the problems of running programs asynchronously.

See manual:

man nohup

Example:

nohup cairo-dock &