Malvina is a huckster, and David is woefully misinformed. Probably, your battery is weak, and if your car starts with a jump, then all is well except your charging system. Put a DC voltmeter across the battery posts, expect to read between 12 and 12.6VDC. Now start engine, and again test across battery posts. Should read around 17 or so. If reading is lower with engine running than when off, alternator is suspect. If not alternator, check ends and connections (where cable connects to lug and where lug connects to contact point) all the "fat" wires -- from battery to starter relay, from relay to starter, and from car frame back to battery. If alternator and fat wires all OK, you have a voltage drain -- now look for a cigarette lighter stuck in, or light that won't go off --- trunk light, dome light, glove box light are suspects.