“一个人”常常用来说自己没有别人陪着，是自己做一件事。

"一个人" is often used to say that you are alone without others, doing something by yourself.

比如你一个人吃饭、一个人在家，意思就是只有你，没有别人。

For example, if you eat alone or are at home alone, it means only you are there, no one else.