1) Singularity
It is also called collapsed core. Physicists call the zero-volume, infinitely dense region at the center of a black hole a singularity. According to general relativity, a black hole's mass is entirely compressed into a region with zero volume, which means its density and gravitational pull are infinite.
2) Event horizon
Event horizon is the opening of Black hole. The defining feature of a black hole, the event horizon is a surface in spacetime that marks a point of no return. Once an object has crossed this surface there is no way that it can return to the other side. Consequently, anything inside this surface is completely hidden from observers outside.
3) Photon Sphere
The photon sphere is a spherical boundary of zero thickness such that photons moving along tangents to the sphere will be trapped in a circular orbit.
4) Ergosphere
Ergo is the greek word used for energy. An egg-shaped region of distorted space around the event horizon (The distortion is caused by the spinning of the black hole, which "drags" the space around it).
5) Static limit
This is the boundary between the ergosphere and normal space. If an object passes into the ergosphere it can still be ejected from the black hole by gaining energy from the hole's rotation.
However, if an object crosses the event horizon, it will be sucked into the black hole and never escape. What happens inside the black hole is unknown, even our current theories of physics do not apply in the vicinity of a singularity.
