Gather is a verb with many related meanings, most involving drawing together or assembling something. You may gather your socks into the laundry bag, or you may gather your thoughts by making a list.
Gather often is used to describe bringing people together for some purpose, like the students who gather in the hallway awaiting an announcement. Gather can also refer to an increase or gain, like when you gather speed and go faster on your bike. Gather can describe coming to a conclusion or an understanding. After listening to your brother's comments and watching him pack up his video games, you may gather that he isn't going to be around for dinner.