There are 8 B vitamins in total, but the ones you might recognise the most are biotin, folate (folic acid) and vitamin B12.
You can also take a vitamin B complex which includes all of the recommended doses of all 8 in a single supplement.
Vitamin B impacts your energy levels, brain function, metabolism, and is especially important for pregnant and breastfeeding women as it aids fetal development and can reduce the risk of birth defects.
Taking vitamin B is important for older men, too, as it can increase testosterone levels which are thought to naturally decrease with age.