andar vs caminar
Both mean 'to walk'. Caminar is the neutral verb. Andar is looser and often means 'to be' or 'to go about'.
caminar
To walk — the physical action, often a purposeful journey on foot.
Camino al trabajo todos los días.
I walk to work every day.
Standard walking.
Caminar es muy sano.
Walking is very healthy.
As a noun-like subject.
Caminaron por el bosque.
They walked through the forest.
Journey or exploration on foot.
andar
To walk, to go about, to be (in a state), and to work (of a device).
Anda por la calle sin mirar.
He walks down the street without looking.
Casual walking.
Anda buscando trabajo.
He's looking for a job (these days).
Andar + gerund = to be doing something over a period.
¡Anda ya!
Oh come on! / No way!
Exclamation of disbelief. Also 'anda' for surprise or encouragement.
Tricky bit
'¿Cómo andas?' = how are you getting on? 'No anda' for a machine means it's not working (common in Argentina). Andar covers many moods; caminar is always on foot.