need help some question please What is reapportionment, and when does it occur? On what data is reapportionment based, and why is it important?

need help some question please 

1. What is reapportionment, and when does it occur? On what data is reapportionment based, and why is it important?
2. What is the VRA, and how does it affect the redistricting process?
3. Is the VRA still needed? Why or why not?

please put in your own words thank you