In screen the terminal multiplexer.
- To split vertically:
ctrlathen |. - To split horizontally:
ctrlathenS(uppercase one). - To unsplit:
ctrlathenQ(uppercase one). - To switch from one to the other:
ctrlathentab
Note: After splitting, you need to go into the new region and start a new session via ctrl a then c before you can use that area.