What is the difference between "andar" and "caminar"?
In the context of "to walk" I believe they are synonymous, although I think "caminar" is a bit more formal than "andar".
However there are lots of expressions and idioms with "andar" that I've never heard used with caminar such as:
¿Qué tal andas? - How are you doing?
¡Anda! No vas en serio. - Get outta here! You can't be serious
Andarse por las ramas - To beat around the bush
I hope this helps you .
Andar has a lot more meanings than caminar. In the drae, caminar has 5 definitions and one phrase, while andar has 19 definitions followed by a list of special uses.
"Caminar" comes from "camino" (path), and therefore it is generally used for specific distances or paths.
"Andar" comes from "ambulare" (around + go), with a much more vague sense of motion, a kind of going and coming here and there. Therefore, it has a lot more meanings that "caminar" ("ambulance" is derived from this verb).