Your system has two spaces RAM and Storage (HDD or SSD or both!)
Let’s think this like water! a cup and a jug. Clearly a cup is a lot easer to drink from then directly from the jug, and once you’ve used what you had in the cup or throw it away you can pour more water into your cup.
So if you need more water at one time than what the cup can hold you just can’t do it. But! If I get a bigger container like a mug! I can hold more water.
So what does this have to do with your system? Here the RAM is the Cup or larger Mug.
The water is your work piece you are working on which could be a large music piece for school, Video documentary you are composing for PBS NOVA or your vision of COVID like Peter Howson the artist And lastly, you are re-writing a major history reference book like the coming fourth edition of History: From the Dawn of Civilization to the Present Day
So… Upgrading the RAM will allow you to have a bigger work piece or multiples active at the same time. For most web surfers and light users 8 GB is enough. But if any of the projects I listed are things you are doing then 16GB of RAM will be useful (there are lots of others too).
Some find 16GB is still not enough! I work on ultra large photo images and I have 128 GB of RAM in my Mac Pro but the CPU and I/O system it has is holding me back. But, thats another story!