To my understanding, take up is the movement of the trigger to the rear until it engages the sear. Military weapons have lots of this even to the point of building in two stage triggers. Creep is the trigger movement from the engagement of the sear until release. A crisp trigger has a minimum of creep. A cheap trigger feels like there is sand in the works. Overtravel is the movement of the trigger to the rear after the sear is released and until it hits the stop or limit of travel. I hope this helps. But there are other creeps too I won't go into here.
Take up is motion up to the point where you encounter resistance from the sear on the gun. It's the "blank" space on the front of your trigger pull until you feel something grab the trigger.
Creep is motion during the sear engagement. It should be minimal on a good gun, but it often is not. It's the movement that you feel in the trigger while there's resistance on the trigger.
Overtravel is the movement in the trigger after the sear has tripped.
Explaining how they affect shooting accuracy would take at least 500 words, and I've got to get to church. Many shooting books talk about trigger pull problems and how they affect shooting accuracy. You should have no problem finding such an article.