The PressFit 4630 bottom bracket is for frames that are non threaded and have a 68 mm width bottom bracket with a 46 inner diameter bottom bracket shell. This is for using a 30 mm crank spindle with the PressFit30 frame. This is a popular bottom bracket standard around the cycling industry. Here you have your choice of Angular Contact steel bearings, ceramics, or XD15.
Note - This is the bottom bracket that works with a BB386EVO shell (86mm wide and 46mm ID) popularized by the brands BH and FSA. If you do not own a BH please disregard as this will not be a Trivial Pursuit question.
For your MTB this can also be your bottom bracket if your frame has a shell width of either 68 or 73 mm and an internal diameter of the bb shell of 46 mm. Once again, with a MTB you only use this product if you are running a crank with a 30 mm spindle.