I have a colleague who's double of my age and sometimes asks questions related to development that I didn't knew 6 years back.  
But given his age and experience, am I doing right to tell him like what firebug, ST3 etc is? He is clever as in, he finds out what other person was saying and answers it with "I was about to say this".

Someone told me he can leave you behind and might get in good graces, because he is vocal and he'll use my knowledge to impress the boss.

I'm confused on how much should I help him and to what extent? When should I tell my manager about his  requests for help, what he is lacking and effecting my work?  

*P.S - I am new at my work, so is he, but I've working here longer.*