What is meant by "CAP EXEMPT H1B"

Does being cap exempt mean that a person can file H1B anytime during the year and does not have to wait till April to file a new H1B ?

If yes, does the person still have to wait till 1 oct to start working on the new H1B or he/she can start working as soon as a cap exempt H1B is approved?

Cap-exempt petitions are not subject to April filing and Oct start date. This means petition can be filed anytime and one can start working even prior to Oct. The actual start date will depend upon whether the person is already in US on H-1 or not.