Dear English learners,
Today I'm going to write about when to use boyfriend, girlfriend, friend or man friend. Have you ever heard of man friend?? 

my boyfriend = the man I am dating, the man I am romantically involved with, the man I'm in a relationship with
my girlfriend = the woman I am dating, am romantically involved with, am in a relationship with

Is that all? No. Some women also use "my girlfriend" to mean their female friend (whom they are not in a romantic relationship with). I don't think men use "my boyfriend" to mean their male friend. They might say "my buddy". 

There's also "friend", "male friend" and "female friend". 
My friend Bill means my male friend Bill (probably not a boyfriend).  
My friend Amy means my female friend Amy (probably not a girlfriend).
You don't have to say "male friend" or "female friend" but those would show they're not your romantic partner, just a friend. 

Recently, my friend mentioned her "man friend". I said is that your boyfriend? I wasn't sure if she meant male friend or boyfriend. She said yes, he is her boyfriend. 

Hope that was helpful and not too complicated!