Hot Network Questions in the right-hand sidebar, the “hot” tab on each site, and on stackexchange.com.

“Hot questions” can refer to two things:

In both cases, questions are included if they hit a large “hotness” in a short time, with hotness determined by score, views and number of answers. The formulas for both cases are different; e.g. questions without answers never appear on the Hot Network Questions, but can appear on a site's "hot" tab.

The "hot" tab of the per-site meta is used to obtain questions to show in the "Hot Meta Posts" block part of the on the main site; for questions about that, use that tag as well. This excludes Stack Overflow.

The network-wide list has further adjustments to avoid being completely dominated by a site, and entire sites can be excluded from the list on a case-by-case basis. Inclusion is fully automatic, but moderators have the power to remove a hot network question after it has been automatically included.

When a question becomes a "hot network question", this is logged in the question timeline.

Useful links