is an out-of-universe category.
Historical stories, also thought of as "pure historicals", are those which are set on Earth, prior to the date of broadcast or publication. However, they do not contain aliens or alien technology, apart from the Doctor and whatever devices he might own or make. A prime example is The Aztecs.
The question of just how much prior to the broadcast/publication date a story must be set for it to be considered an "historical" is an open one. If a Peter Capaldi story were now to be set entirely in the 1970s, and the Doctor encountered no aliens, it would clearly be an historical. By contrast, if a hypothetical Jon Pertwee serial were set entirely in the 1970s, and no aliens were encountered, it would not be an historical, because that's the same decade in which it was broadcast.
Pure historicals can be contrasted with pseudo-historicals, like The Unicorn and the Wasp, in which the TARDIS crew travel back in time to sort out a historical problem, but encounter extra-terrestrials or their technology.
The following 122 pages are in this category, out of 122 total.