Hi Dabidnc,
We use "follow" to refer to travel or move behind something or someone. It also means that we pay close attention to something.
Example: Follow the car in front of you. / Follow the instructions provided by the instructor.
"Follow up" is a phrasal verb which means to perform an action connected with something that happened before. This action can be (i) a continuation of the same previous action (ii) another action to supplement the previous action.
(Follow-up can be used as a noun)
Example:
The hotel manager would like to follow up (phrasal verb) on a complaint by a guest who stayed last week.
As a follow-up (noun), I provide my students with quizzes on a regular basis to assess their level of understanding.
Hope this helps.
Cheers, Lance