Generally speaking, the hashtag #anon is just a rallying point for all kinds of Anonymous stuff.
Specifically, this refers to a single person within the "Anonymous Collective". However, since the "Anonymous Collective" just refers to people in general who happen to be cloaked with anonymity, and the decentralized acts of the "Anonymous Collective" are essentially the collective will of humanity as it is unleashed by the freedom gained by that anonymity. So the "anon" is essentially any human that happens to be cloaked by anonymity at a certain time or place.
So, if #Anonymous refers to the collective will of humanity unhindered by the social program, and #anon refers to a single human acting unhindered by the social program, then #anon really just means "unimpeded human" or something like that. So it's interesting to note that "#anon", for all of it's lack of definition, has taken on quite a super-charged presence on the world wide web. In fact, the hashtag has become such a powerful rallying point that it has come up against resistance. For instance, on Instagram the hashtag "#anon" is essentially banned. It is possible to include it in a post, but it's pointless because it is impossible to search for it. Which is kind of like Instagram banning any unimpeded human from finding The Other unimpeded humans, for whatever undefined purpose they might be looking for each other.
This just generally makes it hard for people who like to buck the status quo, and empower humanity, to gather collective energy with others who want to do the same. Which forces us to do things like create this website so that we can continue gathering that rebellious collective energy in other forms :)
Hopefully that helps explain how #anon can mean so much, although it means so little.