Psychobells

My system has 8 GB of DDR4 RAM, which is the minimum required. I did just order some more to get up to 16 GB, but in the meantime, I'm curious about the RAM usage. My system right now is at 31.3% in use and 58.1% cache, leaving just a little bit extra overhead. Is this cache usage normal or high? How does the cache work exactly/what does it do? Hopefully these aren't silly questions!