My half cousin who is a lesbian mentioned it when she was telling me more about LGBT. I asked her what is it and she told me that I'll find out when I get older. But I really wanna know what it means. Can anybody tell me what it is?
You definitely don't need to be older! It's a portmanteau of "gay" and "radar." It's basically the ability to "detect" gayness in someone, pretty much just by looking at them and seeing how they interact with others. For example, when Ellen Page came out as gay, someone could have said, "I knew it! My gaydar is always spot-on." Or you could say about someone, "He pings my gaydar. He has a girlfriend? I'm telling you, he's closeted." Personally, I'm still waiting for mine to be shipped. I think at this point my gaydar is more likely to be on Mars than anywhere on me.
It is really just based on really good social skills. You can, as a consequence, sometimes pick up if a person is gay, and some people call this ability "gaydar." You can pick up the same ability by just taking time to understand people, and this is hard for some of us. Just take the time to try to understand the people you know. Understand how they think. That is all it really is.