Web architecture explained

Okay, I'm trying to sort out all these buzzwords in web programming, but it gets more confusing the more I read about it.
The buzzwords that I'm trying to understand and how they are connected (the architecture) are:

• web server machine
• web server (software)
• application server
• web application
• servlet container

I'm starting out in Spring (and Spring Boot), so it would be wonderful if any of you'd like to explain the differences between these buzzwords in that context.

Which runs in which (example: does the web app run on the web server or in the servlet container?)

Why is Tomcat called a server in one place, but container in other?