Resident Evil: True Director’s Cut is a patch made by Deli295 for Capcom’s original horror classic that wants to be the most comprehensive version of the game available, adding in a bunch of stuff from earlier Japanese releases that for whatever reason we never got in Western editions.
While the West received numerous version of the 1996 game, including a supposed “Director’s Cut”, none have contained everything that was present in either the Japanese Director’s Cut of the game, nor earlier demo and beta releases. This includes a slightly more explicit intro, a scene where there’s a message written in blood on a wall, and some soundtrack omissions, all of which can now be found in Resident Evil: True Director’s Cut.
Nothing huge, then, but if you’ve ever wanted to play a version of Resident Evil that includes everything ever made for the game—more even than made it into the original Japanese Director’s Cut, since this includes demo and beta content—this is the only way to do it.
You can download the patch here, while below is a 2020 video by Kendozone 켄도 that goes over the differences between the Japanese and Western versions so you can see some of the stuff that is being added.