Bunion (Hallux valgus) refers to a condition where the bone at the base of the big toe protrudes, causing the big toe to deviate towards the second toe. As the big toe starts to bend towards the second toe, the long bone of the big toe becomes misaligned and protrudes noticeably on the inside of the foot, forming a visible bump at the joint. 

Hallux valgus is typically a progressive deformity that worsens over time. Depending on the severity, it can lead to pain, inflammation, and difficulty finding properly fitting shoes.  When the big toe begins to tilt towards the second toe, it can also affect the second toe, leading to deformities like hammertoe or dislocation of the second toe. 

It is more common in women than men, and there is a tendency for it to run in families. In cases involving children, it's crucial to identify and reduce risk factors associated with the development of foot joint deformities to either halt or delay their progression.