Whater Changes?????????????

Ok i no for the fish experts this is probably a dumb question but i just want to make sure i am going to be doing it right i am going to be having a betta and some tetra in a 10 gallon ( I HAVE MADE SURE THAT IT WANT BE TO CROWDED ) but what exactly is a water change and how do you do it and what is what cycling please just give me any helpful info that would help me be a good fish owner ...........Thank You