Third molars/ Wisdom teeth are the last permanent teeth that erupt into the oral cavity
However, in most of the people due to lack of space, small jaws, they fail to erupt into the mouth resulting in third molar IMPACTION

Impacted teeth can cause a number of problems for adjacent teeth, including:
Impacted teeth can push into or crash into nearby teeth when trying to break through the gums, causing damage and sensitivity.
Impacted teeth can crowd other teeth, making them difficult to clean and potentially leading to tooth decay and gum disease.
Impacted teeth can push on adjacent teeth, which can eventually lead to a misaligned bite.
The position of an impacted tooth can create a deep socket between neighbouring teeth where plaque can build up, causing bad breath, gum disease, tooth decay, and infection.
Other problems include difficulty in mouth opening and in some rare cases they result in cyst and tumors.
Impacted tooth should be removed immediately by an Oral & Maxillofacial surgeon to prevent future problems