Hi Teddy, it more than likely means you cannot take your eyes off the gorgeous girl who is your current crush. Some look back and they want you to talk to them. Others are shyer and you may need to do more than stare to get their attention. Of course boys who stare at their crush are admiring them and lucky 'crush'. You got someone in mind, if she fancies you, she will look back and if she does, then approach her, and especially if you want a special friendship with what will be a really good looking - lovely 'crush'.
When boys stare at their crush, is it for their crush to look back so they can talk to them, or are they admiring them?
Simply I would say that it is both, they are looking at their crush because they can't take their eyes off them, as Catherine said. But also secretly I think they want their crush to look at them because they secretly want them to know they were looking, to very subtly try to put the option in their head, or to see their reaction.
If a guy you like stares at you: Look back, smile... Leave the group of friends you're surrounded by. Talk to him. You might find out what interesting things he has to say.