Address Latch was Intel's way of limiting the number of pins on their early microprocessors, to limit the production cost.

Sadly this "feature" remained in Intel processor architecture for several generations, despite the fact that production cost was no longer an issue.

What it does: On the early processors there was an 8 bit bus acting both as an address and a data bus (to save pins). Then there was the ALE (Address Latch Enable) pin, that determined if the bus should act as data or address bus. This of course decreased the efficiency of the processor, because you had to switch back and forth between the two states, according to which bus was needed.