umm thats kinda true i guess, ur alternator does 2 things it spins obviously and engages into the flywheel ring gear which is wrapped around ur flywheel and when that pulls forward it engages ur engine and starts her up, ur starter also clicks forward when u turn ur ignition this is where it actually moves the gear forward to hit the flywheel cuz normally its about half an inch away, when u accidentally turn ur ignition when ur car is turned on that horrible grinding is the gear tearing accross ur flywheel ring gear when it clicks forward. this isnt really ur problem though buddy, ur engine is turning which means that ur starter is working fine, ur battery may be discharged so that the engine isnt moving fast enough to be self maintained but more likely its a fuel air spark issue, ur alternator charges ur battery, theoretically u don't need an alternator if ur battery is fully charged (some dragracing cars run without them because their runs are short enough to just charge the battery every few times or so). so as long as ur battery is charged up ur alternator doesnt make a difference (obviously if ur alternator is crap and ur battery discharges all the time its quite a PITA). i'm telling you check ur spark plugs, plug wires, cap and rotor, charge ur battery up all the way (even if its new some batteries are defective take it to where u bought it and have them charge it and test it while they are at it) change ur air filter if needed. let me know if u need more help