Hola Emanuel
Andar and caminar are interchangeable, however I would say we tend to use more verb "andar" when we refer to the more "mechanical movement" and "caminar" when we add an objective or a time phrase, for example:
Siempre voy al trabajo andando. (I always go to work on foot [walking])
Ayer caminamos durante horas. (Yesterday we walked for hours.)
Fuimos caminando de un pueblo a otro. (We walked from a village to another.)
But as I said, they are interchangeable. This nuance is minimal...
Hope this helps,
Inma
