Lubuntu and Ubuntu are basically no different in the execution of the OS. They are differently when it comes to GUI and applications.

Swap space is the area on a hard disk which is part of the Virtual Memory of your machine, which is a combination of accessible physical memory (RAM) and the swap space. Swap space temporarily holds memory pages that are inactive. Swap space is used when your system decides that it needs physical memory for active processes and there is insufficient unused physical memory available.

You should use a Swap partition.

Here is a ref for you https://help.ubuntu.com/community/SwapFaq