How do hair extensions work? and how much do they cost?

hair extentions are weaved like stitched into your own hair, or they can be glued into your hair.{ hairline}. if you have a sally store in your area you can buy them there.they are somewhat cheap. look on e-bay they have them too. i already have really long hair, but the extentions can ruin your hair like when taken out your hair falls out with it. they are hard to manage as well. you should do a research on them before considering to get them. good luck.