Let me first explain the concept of Trail Braking (Front brake). Trail braking is using your Front brake before entering a turn to not only slow the bike, but also to keep brake pressure applied to compress the front end down to help carve the bike into the corner(creating more contact tire patch), which in turn creates faster entrance and exiting corner speeds.

I will give a detailed explanation from a diagram listed below (Rough Draft) which will include a Left 90 Degree Turn. I will explain points of entry and detailed description of brake application that consists from braking cones laid on the track as well as pressure applied during entry of the apex and transitioning to the exit of the turn! 

We will start by transitioning our bikes to the right hand side of the track to prepare for the left hand turn. As you approach the braking cones(* Symbol on Diagram) you will be applying HARD pressure to drastically slow the bike down, this will in turn compress your front end down (Red Diagram Line). 

This is where trail braking takes place. Now in order to keep the suspension compressed you need to keep the brakes applied.  As you start to transition yourself (Blue Diagram Line) into the corner shooting toward the apex (@ Symbol on Diagram), you want to go from HARD brake pressure to gradual FEATHERING brake pressure. This will keep the front end down and carve the bike without drastically slowing the bike.

After you hit the apex of the corner(Green Line Diagram) this is where you will let slowly off the brakes completely and start to GRADUALLY apply Throttle to exit and increase speed. Shoot Towards the outside of the track from here!

Now the reason why using this method increases corner speeds, think about it you are now slowing the bike to corner instead of slowing the bike then cornering ! A Friend once told me (Mickey), if you were to go outside to your bike and compress the front end down (Suspension). You will notice it squashes the front tire down it creates more side wall patch (Contact Patch), this allows faster cornering as well.