I'm reading their Signals article on their wiki, and it's still not 100% clear to me.
I'm trying to (and failing) to understand the Entry signal, (and subsequently, the Exit and Combo signals, because Exit "Works the same as Entry but..." and Combo "Combines Entry and Exit").
So here's what it says on Entry signals:
Block Entry Pre-signal
An entry pre-signal prevents trains from entering the following block, unless there is at least one green exit signal on the opposite side of the block. This prevents trains from entering the block until there is an available exit and obstructing it. Note that depots have a built-in two way signal (it works as an entry pre-signal in a pre-signal set). If there are no signals designated as exits on the block directly behind the entry pre-signal, it behaves as a normal block signal. This is convenient for bi-directional pre-signals where only one direction needs pre-signal functionality.
Can anyone please provide a clearer explanation, and perhaps tell me how do Exit and Combo relate to it?