Entity Field and entity collection Field

Hi, I Have been reading the API document. I was able to create entities with text and single-select. My question is what are entity Field and entity collection Field? I still can’t seem to wrap my head around this. Do you have more concrete examples on how these correspond to the UI? Thanks!

Entity fields and entity collection fields correspond to the relationships between types. A collection represents a one-to-many or many-to-many relationship.

Ok thanks Chris