It depends on the contest. It can mean nice, cute, good, pleasant, courteous, sweetheart, darling, dear and so on.

It means darling.

Cute. Ohh wait, It's coming from a girl, it can mean anything )

It is depend on situation If you use this adjective to discribe something or someone so it's mean "nice, pretty " But very often women use this word to applay to sweetheart and it's mean" darling" For example Милый дай мне яблоко -My darling give me an apple

I do not quite agree with previous answers. The word 'Милый' primarily means 'Cute' or 'Pretty', like a cute baby or stuff like that. If a girl says 'Ты милый' to you during a correspondence, she probably wants to say that 'You're sexually attractive', but she's trying to not to say that straight and she's trying to hide the real meaning by saying something else, like 'Милый'. Or 'Ты милый' may also mean 'You're nice to talk to'. I often hear girls say 'Он такой милый' or 'Познакомь меня с тем милым парнем' and they obviously imply that the guy they are talking about is very attractive in a sexual way.