What do “watched tags” and “ignored tags” do?

Question

What are watched tags and ignored tags? How do they work?
What are tag subscriptions?
What are interesting tags?
On Stack Overflow, the content of the main page question list appears to be influenced by watched and ignored tags. How does that work?

For more information, see "How do I find topics I'm interested in?" in the Help Center.

13 revs, 8 users 31% · Accepted Answer · 2021-01-18 11:45:57Z

Watched Tags

To watch a tag, do one of the following:

Note that you can use wildcards in the latter three.

This has the following effects:

Questions with these tags become highlighted on the front page.
Questions with new activity are shown on stackexchange.com/filters.
In the review queues, questions from these tags are shown to you before other questions.
The search operator intags:mine limits search to questions with those tags and answers to such questions. If your “Watched Tags” list is empty, the search operator does nothing.
On Stack Overflow, this affects how questions are displayed on the home page (Recent questions) and the various questions pages.

Also known as followed tags; formerly known as interesting tags and favorite tags.

To ignore a tag, do one of the following:

Note that you can use wildcards in the latter two.

This has the following effects:

By default, questions with these tags are shown faded; they are still visible but less prominent. It is possible to hide them completely, for more details see: How do I hide posts matching my ignored tags?
On Stack Overflow, this affects how questions are displayed on the home page (Recent questions) and the various questions pages.

To subscribe to a tag:

This will cause you to receive mails about activity in those tags.

Note that you can also obtain RSS feeds of recent activity on a tag at various places.