It's important to note that the singularity is a theoretical point and not something that is directly observed. Our current understanding of physics breaks down at the singularity, so we don't have a complete picture of what it was like.
Here's what we know about the singularity:
* Infinite density: The singularity is thought to have had infinite density, meaning that an infinite amount of mass was compressed into an infinitely small point.
* Infinite temperature: The singularity is also thought to have had an infinite temperature.
* Zero volume: It had no size.
The Big Bang theory describes the expansion of the universe from this incredibly hot and dense state.