what is the importance

Orlando is where Tea Cake is from, and he and Janie also go there for fun.

Tampa is where Who Flung is from, the man who deceived Annie Tyler, convinced her to move to Tampa, and then stole all her money.

I am not sure about the other two places.

belle glads is where Janie and Tea Cake move to because it's apparently a fun place, the people there are lively. It is here where Janie somewhat re-enters society by getting a job picking beans with Tea Cake. Janie transitions from a trophy wife that Joe Starks moulded, into a equal where she participates more in the community.