Anonymity is the absence of Identification (or Onymity), it is when individuals are indistinguishable from each other, they all look the same.
In short, Anonymity means you are not identified. In this example, Someone hid their identity, and is talking to Alice. That someone is anonymous until Jack can figure out who that person is.
Anonymity is extremely fragile when that Someone is not implementing strict OPSEC practices, relating to:
Using the correct Technology: (What is that Someone using, to protect their Anonymity ? (A mask, a Coat, a mask / the Tor network, i2p, etc))
Using the correct Behavior: (By that Someone's actions, they are not revealing who they are. (They are not saying they are Walter Hartwell White living at XYZ)
DISCLAIMER: That Someone remains Anonymous UNTIL THEY MAKE ONE OPSEC MISTAKE !
Keep in mind that maintaining Anonymity is a much stricter practice than that of maintaining Privacy, as you will see, more threat vectors come into the picture.
The first the and foremost enemy of Anonymity is Surveillance of any kind. Privacy is a REQUIREMENT if you want Anonymity.
Example:
Jack is surveilling Bob 24/7. He sees that Bob purchases a mask and a coat, He sees that Bob wears the mask to then go outside to do something sketchy.
Conclusion:
Because Bob did not have Privacy from Jack in the first place, Bob cannot have Anonymity either.
Surveillance CANNOT be tolerated when you want Anonymity. So before you try to learn to be anonymous online, learn why and how to get Privacy online here.
The other major enemy of Anonymity is Know Your Customer (KYC) Procedures, these are ways for services to force their customers to identify themselves, wether they like it or not.
Example:
Jack owns an online service (such as a centralised crypto exchange), he accumulated a large userbase over the years, over 1000 active users. The government where Jack operates is ramping up their financial regulations on businesses, and now Jack is being forced to identify all of it's users using standard KYC procedures
Bob (an user on the website) that was anonymous up until that point, is now forced to do the following if he wants to keep using the platform:
1) state his real life name
2) his date of birth
3) his home address
4) send photos of his identity card
5) send photos of his face (facial left, front and right sides)
Conclusion:
Jack is either forced to identify his users or go out of business
Bob is either forced to identify himself or stop using the service
All of it because the government intends to destroy Bob's right to remain Anonymous online.
But the root cause of surveillance and KYC procedures, is that every centralised entity (any public or private business) will be eventually forced to comply to their government's requests, at the expense of their users.
There are only 2 possible long-term outcomes for Centralisation:
Act as a governmental proxy to enforce regulations/agendas, at the expense of users' rights
Or be forced out of business altogether.
To be able to achieve Anonymity, you need Privacy, and at least some level of Decentralisation (in the case of anonymization networks like Tor for instance), as we will see in our next tutorials.
In a way, Anonymity is an improvement over Privacy. In the sense that Privacy is about being about to seclude yourself or information about yourself. Anonymity is the logical next step to Privacy, Where you not only just conceal what your actions are, but also who you are.
Depending on the context, especially if you are living in a dictatorship, Anonymity is vital for you to act freely, out of the grasp of adversaries.
As we have discussed previously, for a government's laws to be respected, they need to be enforced.
And for the laws to be enforced, governments need:
To know what happened (lack of 
Privacy, using Surveillance )
To know who did it (lack of 
Anonymity, using KYC procedures )
Governmental control as a concept itself rests upon these fundamental 2 pillars, the detriment of the individual's Privacy, and Anonymity.
In order to regain the control you lost to dictatorships, you first need Privacy, and then you need Anonymity.
Most governments want to control the public opinion through opression and censorship, Journalism is one of the most demanding sectors in terms of Anonymity, especially in authoritarian/dictatorship governments where censorship is omnipresent, for them, very sadly, Anonymity is the difference-maker between life and death in those areas of the world.
For instance, the Freedom of the Press index is a great indicator to tell if you are living in a country that employs censorship as a means to control the population or not. Make no mistake, Governments are often ready to murder journalists to protect their public image, like in Mexico: [1] [2].
Essentially, the idea is to reduce your attack surface as much as possible, given the context of near-omnipresent surveillance, Privacy has it's limits, and Anonymity very often becomes the only way out of opression. If noone knows who did something, there can't be any repercussions for the perpetrating party.
In a way, Anonymity is superior to Privacy because whatever happened may have been hidden thanks to Privacy, but it may be discovered at a later point in time. Anonymity on the other hand, if maintained, remains a permanent way to act without any repercussions.
Until there is Nothing left.
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Contact: nihilist@contact.nowhere.moe (PGP)