A "get-together" is 1. an informal and usually small social gathering. 2. a meeting or conference. It is can also be used to mean a reunion of sorts. e.g. I And Lisa organized a small get-together of our family members. My school friends were thinking about a get-together this summer.

It's any kind of social gathering, like a party, a dinner party, a cook out, etc. It's fairly informal.

It means meeting, a place where people meet.