1. I'll treat this seriously:
I hope you can see how that means the same as the term I believe you Euros use, as in: The worlds most popular soccer "club", Manchester United, is owned by an American.
Much like "club" has more than one usage, including similar usages, so does franchise.
Now you can comment out of knowledge, instead of ignorance! Yea!
2. Generally teams don't move around.
There are 5, iirc, teams out of 32 (I think, I forget) that have moved, 2 of which took the name of the team with them, and one (The Cardnials) have moved twice. As a rule of thumb, a team moves about once every 15 years.
But for example, the oldest teams in the NFL (Bears, go bears, and the Packers, circa 1919) have never moved.
Why they move? Lots of reason. Generally due to wanting a new stadium or lack of support in thier home town.
Mainly tho, they keep trying to put a team in LA (huge market), but they don't care, so they move the team to a city that likes football.