Everyone is oh so curious about this. I feel everyone wants to just know about them even if they are not interested in having them. Few things. There are different techniques to do so. I will briefly discuss some if you are contemplating on getting them. For some it will look great, others not so great depending on body type, face structure, etc. Some think you need extensions to add length when you can really add them to help with some volume in the hair. Depending on hair length you already have, it may help it out a bit.
Hope this helps!
Bonded: Hair is glued onto individual hair strands. Grows naturally with the hair.
Pro: Natural looking. Long lasting
Con: Tangles a little bit at times at the scalp. Takes time to apply & remove.
Pro: Not too much damage. Easy to remove.
Con: A little painful. A little more upkeep (roughly every 4 weeks). Not long lasting
Clip-ins: clips sewn onto human hair which will clip into hair.
Pro: Easy to remove and to apply yourself.
Con: Can’t really sleep with them in. Will want to remove them too.