Jenkins

Question 1

where does Jenkins run?

Answer 1

Locally, usually Port 8080/8081, can be accessed through browser

Question 2

what is a Jenkins Job? What is a pipeline?

Answer 2

A Job is a very easy command that is run, e.g. execution of a bash script.
A pipeline is more complex, can be used for entire CI/CD streams and can be written in declarative or scripted syntax, both DSLs