There is a variety of routes into teacher training from your traditional University course through the School Centred Initial Teacher Training route (SCITT) that often encompasses the School Direct programmes to the Teach First scheme and so on. To explain the different options and give a comparison of similar courses please read below.
For an overview of teacher training courses please visit Introduction
For details of self-funded courses please visit University v School Direct (non-salaried)
For details of courses attracting a salary while you train please visit School Direct (salaried) v Teach First
For other alternative route please look at Troops to Teachers and Researcher in Schools