Brake hold is a feature where when you are stopped and in drive, the car will hold the brake until you hit the accelerator. The idea is that in stop and go traffic, or at a red light, you can stop the car and then remove your foot from the brake and the car will hold it's position rather than creep forward.

I think they're referring to Hill Assist. In manual cars if you let your foot off the brake you start to roll down hill. This is dangerous if you're parked or stopped facing uphill with another car close behind you.

For generations, this was a problem that people had to deal with, and it took some skill. About 15ish years ago manufacturers started putting a feature on that would automatically hold the brakes until your foot hit the gas.