If there is enough mass to overcome the forces, as mentioned in the previous post (Formation Of A Black Hole), then gravity will win and everything will be compressed into an infinitely small space called ‘Singularity’.
Outside the Singularity, there is a boundary called the Event Horizon.
It is impossible for us to look at anything that lies within this boundary because past this point, the gravitational pull is so strong that not even light can escape it. Hence, Black Hole!
If you were to pass the Event Horizon, it would be a very strange world.
If it was a relatively small Black Hole, you would be instantly spaghettified.
The gravitational pull on your feet would be much greater than gravitational pull on your head and your body would actually turn into a spaghetti like shape.
With more massive Black Holes, such as the one at the center of our galaxy, the gravitational tidal forces are a lot less severe, and so you would be able to survive.
We can’t really be sure about what you’ll see or experience inside, but be sure about one thing, it would be pretty amazing.
P.S. Will give a theoretical view of the inside of a Black Hole soon! Stay Intrigued.