Nah, that's not how it works ! I have over 10 applications and half of them have databases, and that's the prime objective of containers ! Less resource intensive and easier to deploy on low end machines. If I had to deploy 10 VMs for my 10 applications, my computer would not be able to handle it !
I have no idea how it works underneath, that's a more technical question on how container engines work. But if you searx it or ask chatGPT (if you use this kind of tool) i'm sure you will find out how it works :).