The event horizon is the point of a blackhole's radius where its gravitational force exceeds that of an object travelling at the fastest theoretical speed. It essentially means that its the point where escaping the gravity of the black hole becomes "impossible". The singularity is (or maybe isn't) the impossibly dense matter at the very centre of the black hole. The concept of an event horizon means that the exponentially increasing gravitational force towards the centre of the black hole compresses the macro components of atoms together, which relatively speaking, is insane. Have a look a size comparisons that show how far away an atom's electrons would be if the nucleus was the size of a baseball.

-this is all just me trying to recall my black hole phase of youtubing... so i could be way off base