Wisdom teeth or third molars usually appear, or try to, in our late teens. The majority of us do not seem to have sufficient room for them to erupt into proper position and alignment. Genetics plays a role in this. The genes for the size of your teeth is on a completely different chromosome than the gene for jaw bone size. Depending on what your parents have and the combination of these chromosomes you inherit, you may or may not have a mismatch in tooth size vs. jaw size.
For some there is plenty of room and they line themselves up with the other teeth. For others there may be barely enough room and they only partially erupt through the bone and gums (partially impacted). These can be difficult to maintain and may produce gum problems. For still other people with even less room, these teeth may stay completely buried under the bone (total impaction) and often we can just leave them alone.