1. He isn't going anywhere in life.
If your boyfriend does nothing but sit around and play video games all day, never went to college or got any sort of special training at all for a career, still lives at home and has no foreseeable future, then you are dating a boy. A man has ambitions, dreams and goals - and he hustles to work for them.
2. He never plans anything or takes any initiative.
Are you the one who is always suggesting things to do? If so, you might have a problem. A relationship is an equal partnership, and there's nothing equal about always being the only one to plan dates. A mature man will take the initiative to plan a date, too - even if it's as simple as dinner and a movie. And no, saying "come over and watch Netflix" doesn't count as "planning something."
3. He criticizes you and puts you down.
You aren't beyond criticism. And if you do something that is wrong or rude, you need to be called out. However, there is constructive criticism, and there is just flat-out unnecessary and inflammatory criticism. If your boyfriend does things like criticize your body, or your friends, or your job or anything else important to you, for no reason? That's not OK. A boy will put you down to make himself feel better about his own shortcomings and insecurities. But a man will lift you up because nothing makes him happier than seeing you happy.
4. He agrees with everything you say.
Criticism is dangerous if it isn't constructive or kind. But do you know what's even more dangerous? Somebody who never challenges you. Somebody who thinks everything you say and do is perfect. That's the sign of a boy. A boy will blindly worship you and agree with everything you say. A man has his own opinions and beliefs that he feels strongly about, and he will stand up to you and disagree with you if you say something that contradicts those.
5. He's bad with your parents, or friends.
A man realizes that the people who are important to you, should be important to him too. A boy will avoid your parents at all cost, and will not try and get to know your friends. But a man will remember your friends' names and things about them. A man will suggest he spend some time with your parents. A man cares about the people you care about.
6. He never takes responsibility for his part in things.
If your boyfriend is talking about why his other relationships didn't work out, and he never once mentions himself, then you have yourself a boy, not a man. It takes two to tango, and nobody is blameless. This also applies to losing friendships, being fired from a job, etc. A man recognizes his mistakes and shortcomings and owns up to them, instead of blaming somebody else.
7. His life revolves around you.
Outside of you, does your boyfriend have friends? Friends he sees or talks to on a decent basis? Does he have any hobbies or passions besides you? My mom has a name for guys who don't - she calls them "puppies." Puppies will make you the center of their universe, they will follow you everywhere and will make everything about you all the time. Don't date a puppy, date a human. A human with their own life.