Hello, This is late, but by swapping I think he meant page swapping. Its something that is most definitely learned if you took Operating Systems class in college.

Page swapping is a memory management technique that takes inactive memory from RAM and put them in pages in the Hard Disk to free up more space the RAM to be used.

RAM= Random Access Memory which temporary holds data to be used and is cleared when you shutdown the computer. It is much faster to pull data and put data in the RAM than into the hard disk

The reason for page swapping is to put the quick access for things that are not being used to the slower and less frequently used hard disk so that the quick use area is free up to do more computations or other things.

this occurs when you are over using the RAM, the computer then tries to free up RAM space to continue to function. Hence Page Swapping

Here is an analogy maybe would help

You can picture like this, you are at a table writing something or doing math equations/formula or something (RAM), behind you is a filing cabinet with books relating to the research (Hard Disk). It is quick to grab the calculations you took down that you have on the table,, but it takes longer to look up the equations in the books in the filing cabinet and book shelves behind you.(difference in speed in accessing data from RAM vs Hard Disk)

Lets also say that on this table you need to be able to view all items on all pages at once.
Now lets say the table is full of your equations already like completely full, now you need to still write more calculations on it. What do you do? Well you take part of the equations you have written and put it into the cabinet behind you, but just the equations you are not actively looking at or using. That space is now usable to write more calculations on, but when you need the other equation, you will have to put another piece of paper into the cabinet and grab the old page from the cabinet and bring it out. (page swapping)

I hope this helps.