Need a quick explanation

Think of a spool of thread. If you pull the thread the entire spool turns. Both ends of the spool are turning equally to each other.

With a spool, you give up the differential action that is very desirable for the street. Spools are fine for going straight and provide 100% torque to both wheels, but while turning, where one wheel is is traveling a different distance and speed, problems can occur (Premature component failure and/or loss of control).

If you run a spool on the street, you will want stronger, after-market axles. You will also need to be aware, and make others aware, that may drive your car, that it has a spool and may not drive as they expect.