What does it mean when someone keeps to themselves?

It means that you have to be patient with them and let them take things at their own pace and in their own time.

Means they are more comfortable by themselves than around people.

They have their own life it live and problems to deal with

it means they are most likely an introvert and are comfortable being alone. the best thing is to give them distance but if you are interested in trying, try to make convo....MEANINGFUL convo. no small talk. if you know something about them, ask about it. show interest ONLY if you are actually interested. we dont like convo for the sake of noise

Depends on the person.
For me personally, it's because I'm naturally a private individual...

I don't have much contact with other people, I don't talk much irl. I don't get many visitors, but idc. I don't go out much, especially considering it's rained 13 days in a row at some point in the day or night. I only talk to a few people on the phone & I don't like texting (people always reply when I'm driving (no I don't txt & drive,if it's important I'll stop in a parking lot to reply).

I think if you took all the people who keep to themselves and studied them you wouldn't find one unifying reason they do it or a theory that says when someone keeps to themselves it means this or that. rather I think you would discover that each one has a different reason for being like that.

It can have different meanings depending on the situation. Some people prefer to be more to themselves... other times, it can be depression.

They don't want to be bothered. That's just me. No, I am not a serial killer or something.

It means they enjoy privacy,they avoid drama

They a freak in bed

They could be working on something important, and don't want to be distracted. They could be quite smart.

I tend to be very quiet, rarely am I ever boisterous. Alcohol can help loosen me up, but I don’t like it anymore

It could mean any number of things, from the person being a misanthrope (not liking the company of others), to shyness, or simply being preoccupied at any given time.

If you have 2 ears, you should listen twice as much as you speak.

What an amazing question? Thank you for asking..(;