Space diving, explained

It's been 10 years since the first human travelled faster than the speed of sound in a free fall from space. Felix Baumgartner reached the stratosphere and from the edge of space, 36 kilometres above sea level, via an aircraft attached to a balloon.

But the altitude record that Felix broke 10 years ago no longer stands. Alan Eustace has, since, made a free-fall jump from an altitude above 41 kilometres.

So, what exactly is space diving?