Basically a MUX is an online environment where you can create and then roleplay a character, using text. Roleplaying on a MUX is similar to doing collaborative theater with the other roleplayers, and also similar to collaborative fiction writing. You will often see people talking about roleplaying in theater terms. For example, the parts of the online world that have been fully described, and are available as locations for interacting are called the 'onstage area' of the game world. Similarly, a roleplaying session is often called a 'scene'.
Low fantasy means that magic and the gods are real, but all player characters are human.
The setting is the fictional island of Tilana, off the coast of Europe, southwest of the British Isles. The time is the early 15th century. Tevera draws people from all over the island. There is some basis for this reputation. The Crown city is at the center of the frequent conflicts between the Church, the native polytheistic faith, the Crown, and the Counties.