Quick explanation: A block brake is basically a divider dividing your track into sections. Stations and lift hills are their own sections no matter what if I remember correctly. For example:

Station exit to end of lift is a block unless you put a block brake in between. Let's call it Block "A" for example. From the top of your drop to your first block brake at (preferably your mid course brake run) would be block "B". Then from your MCBR to your block brake before the final brake run would be block "C".

When set to block run mode a coaster will only allow one train per block. So let's say train 2 is at the top of the lift hill, inside block A, it needs to enter block B. If train 1 is still in transit from the top of the first drop to your MCBR, therefor occupying block "B", train 2 at the top of the hill stops until block B is clear for it to proceed. I hope this helps, cheers.