So we agree.
There was "the" singularity.
The singularity is basically a description of "nothing." As our language (and cognitive ability in general) lacks the capacity to speak of things existing or happening without space or time, then (if time had a beginning) we can either not talk about anything before the big bang, or we can come up with something to refer to what the big bang came from. Our world, as we normally experience it, is 3 dimensional. The fact that we can relate space and time via the speed of light allows for another dimension (at least) of our experience, but for most intents and purposes. 3d works. We're also comfortable with the notion of 2-dimensional space or 1-dimensional space (it's easy to picture a flat surface or a line, or points on a plane or a line). However, it's much harder to imagine 1000th dimensional space even though from a mathematical/geometical standpoint this isn't a problem (although graphical depictions of such spaces obviously differ from the coordinate plane or a 3d space).
The same is true when it comes to 0-dimensional space. The singularity was a "point" with no volume and a reality without time. In otherwords, to say a 0-dimensional point was anything is basically a contradiction.
What does "essentially" nothing mean ?
It means the big bang theory traces the origins of the universe back to a point when it began to expand. This "point" "had" no mass, no matter, "existed" in nothing and of nothing. I put the square quotes around the verbs because for some action (like having or existing), to occur, it requires time, but there "was" not time.
For example, would you call gravity or a magnetic field 'essentially nothing' ?
No.
If it has a name, "the singularity", it is some kind of something, or why call it "the singularity" ?
Because that allows us to talk about the "point" from which the big bang expanded.