What does it mean if someone is a +1

Here is an example of it in a dating profile

Here are the quick and dirty facts so you can get back to clicking through my photos: I’m a terrible liar and an excellent +1. You can usually find me managing my investments, hitting the gym, or catching up with a friend over cocktails and tapas. And I’m incredibly judgemental…when it comes to T-bone steaks. Otherwise, I’m pretty easygoing.