Text-adventures are exploration games which accept input from the player as typed commands like "get lamp" or "examine table". In addition to a niche-but-dedicated following, they are also a popular 'first game' by novice coders.
Text-Adventure games are named after the original 'Collossal Cave Adventure', which due to sharing and renaming was more commonly known as 'Adventure'.
These days, they are largely considered a subset of Interactive Fiction, as modern authors feel the genre has outgrown the phrase 'Text Adventure'.
A Brief History: The ADVENT of an Era
In 1975, Will Crowther decided to combine his interests in Programming and Cave Exploration and created the original text-adventure game; '* Colossal Cave Adventure*'.
Due to its popularity it was widely copied and frequently renamed: 'Adventure', 'Advent', and 'Dungeon' were the names it was most commonly known.
The popularity of the game led to more than mere copying; Games in similar styles and interfaces were created. Two of particular note were 'Zork', which led to the creation of Infocom and their numerous contributions to the genre, and the Z-Machine they created to port it (which is now a De Facto standard). The other was Roy Trubshaw and Richard Bartle's MUD1 in 1979, which spawned the genre of MUDs, and is considered the precursor to modern MMOs.
Interactive Fiction: The Modern Era
The commercial creation of Text Adventures and Interactive fiction largely ended in the 1990s, but many of the fans continued to be fond of the genre, thus leading to an era of non-commercial and Fan-created games in the genre, as well as regular competitions.
This led to a surge in the number of released titles...and in associated difficulties with cataloging them all, increased complaints about the limitations of the aging z-code formats, and issues with distributing "extra assets", such as sound and graphics.
The Result was the 'Treaty of Babel' and the creation of the Blorb file-format, which allowed wrapping Bibliographical data, a unique ID (called an IFID), Sound and Graphical Assets, etc. into a single file, as well as the Glulx machine specification.
The massive expansion of both the number of titles in the genre, and the breadth of topics and styles covered by those titles meant that it was widely felt that 'Text Adventure' didn't really cover it anymore. Eventually the community settled on the moniker Interactive Fiction, in spite of initial concerns that it was unnecessarily formal (if not out-right pompous).