Look - to look at something for a reason, with an intention.
‘Look at that strange man.’
‘Look at the pictures I took on holiday.’
See -to ‘see’ something that comes into our sight that we weren’t looking for.
‘Did you see that bird? – I wasn’t looking for it, it just appeared.
‘I saw you driving to work today.’
Watch - to look at something carefully, usually at something which is moving.
‘Watch TV’- the TV doesn’t move, but you watch the moving images carefully.
‘Watch here you are going! You almost stepped on my foot!’