My car clicks when trying to start it, the lights & radio come on still, is it the starter or the battery?

WILL IT JUMP START?

REMOVE and clean and reinstall BOTH battery connections. Then TEST with voltmeter before and watch battery voltage drop , while helper is cranking(or in this case -trying to crank)...What does it do? How many volts IF below 10.5 , CHARGE with battery charger (not off another car) and try again later. Test for voltage when key is in crank position , with helper , should get full batterty voltage , if yes , suspect faulty starter , if no- suspect wiring/switch fault.