Ringworm is actually a fungal skin infection. It likes warm, damp skin, and eats the keratin on our skin.
You catch if from physical contact with the infected area of a person or animal that has it, or from sharing towels and clothes.
It can be caught very easily but luckily it is really easy to treat too: just get an antifungal cream from a pharmacy. You just need to be careful coz dermatitis and ringworm can look really similar and be confused. Dermatitis is an allergic reaction and is not contagious.
You can catch ringworm from other infected people or from their towels or clothes, which may carry the fungus (not a worm like the name suggests). If you catch ringworm from an animal (cats or dogs most usually) it is called a zoonotic (I’ve always liked that word) infection.
There are different types of fungi involved and they affect different areas of the body. You’ve probably heard of Athlete’s Foot but “Jock Itch” is also a form of ringworm affecting the groin, and is particularly common among sports people.
There was an Irish Old Wives’ Tale that the seventh son of a seventh son had “the cure” for ringworm and people would travel from miles around if afflicted. See my answer to your dreams question for my opinion on that particular brand of pseudoscience (https://healthn12.imascientist.ie/answer/?p=1207).
Curiously, in other cultures, particularly in South America, the seventh son of a seventh son is believed to be born a werewolf. So maybe you could catch the ringworm from an Argentinian seventh son of a seventh son and be cured of it by an Irish seventh son of a seventh son…