The working memory (or short term memory) holds what you are currently processing. The items stored in this memory are there only temporarily and can be pushed away when you want to store other information. Those memories vanish quickly and you have to repeat them to keep them in your working memory. Scientists assume that you have four slots where you can store items. Those items can also be chunks. Chunks are compact packages of information that are easy accessible for the mind. They are parts of a bigger picture, and you can connect them, which gets easier the more of them you have. See also how to form chunks.
The long term memory is your brains warehouse. It is huge and the course doesn’t even mention an upper limit of what it can store. It takes some time and practice to bring things into the long term memory (consolidation). Once an item or chunk is in your long term memory, you can recall into your working memory. Be aware! Those items will be reconsolidated to your long term memory and can be altered. Thus, your memories live.