I am technologically challenged - do I have to have a phone line/cellular on an apple watch or can all the other functions work via bluetooth?

A GPS only Apple Watch can do Everything the cellular model can do as long as your iPhone is nearby

What the Apple Watch GPS-only can do without an iPhone (there is information about the cellular model as well)

https://support.apple.com/en-us/HT205547

https://www.imore.com/heres-what-apple-watch-can-do-without-iphone

How to use your Apple Watch without your iPhone nearby - "If you don't have your iPhone with you, learn what you can still do with your Apple Watch."https://support.apple.com/HT205547