"Ad blockers" or, more generically, "content blockers" allow users to choose which parts of webpages they want to load or see. There's a debate about whether it's okay to "block" advertisements in this way, since the advertisements provide revenue to the site owner.

Something I never see mentioned in these discussions is that content blockers don't actually "block" content.

The basic model of the web is pull-only. Servers can't just send you messages because they want to (unless they convince you to run a program that lets them); you have to ask for those messages. When you go to a website in your web browser, here's basically what happens:

1. Your browser sends a request to the server for the webpage.
2. The server sends you the webpage (an HTML file). This page contains links to other files, which the server is suggesting you should also have to complete the page. (For example, these might be themes, images, advertisements, and JavaScript code.)
3. Your browser dutifully requests all of these additional files and gets them from the server. (See step 1)

When using a content blocker, you tell your browser not to make some of these requests. You are the one requesting the content (the server just asks you to request it), and you can choose not to request it.

I often use the mail as an analogy for the internet. In this analogy, the paradigm of advertisements on the web seems ridiculous. Suppose you send a letter to a person or organization asking for some information. They send you back a letter. Their letter includes a list of advertisers and asks you to individually mail each of them to ask them to send you back advertisements in the mail. The letter asks you not to read it until all the advertisements have been returned and opened.

Would you request those advertisements? I wouldn't! It's a ridiculous request! Why would I voluntarily ask advertisers to send me ads? It's inefficient, and it results in the thing I want least out of this exchange: to have to see ads.

So, to reiterate my point, ad "blocking" isn't actually blocking the ads at all; it's refusing to ask for them.

Now, content "blockers" may also prevent your browser from executing (in the case of web programs like JavaScript) or displaying some parts of the page that are actually part of the webpage. This should also be your choice. If someone sends you an envelope containing a letter and also another envelope, you don't have to open the second envelope. If someone sends you a list of instructions ("Please write us back to tell us all your private information while you read this letter"), you don't have to follow those instructions. When someone sends you a webpage file, they have given you something. It's yours now. If you don't want to follow some instructions in the letter, or you want to redact parts of it, that's your prerogative.

If you get a piece of mail, and you don't open it, have you "blocked" that mail? No, you just chose not to open it. If you get a piece of mail that contains instructions to request further pieces of mail, and you don't follow those instructions, have you "blocked" those further pieces of mail? No, you just chose not to request them. These things aren't thrown at you; you're not blocking them. You're the one with the agency of deciding what you want servers to give you and what you don't. Ad/content "blocking" is really all about giving you back the power to choose how to engage with your "mail", so to speak.

Now, some people might want to mail in requests for those advertisements because they know it will help their correspondent get some money. That's fine, as long as their correspondent can be trusted not to partner with abusive ad companies that might send you tracking devices (web trackers) or anthrax (malware) in the mail. But they should know it's their choice to mail in for those ads.