What exactly is latch?
Latch can be used as a noun or as a verb. You got it right. 
ALE - Some IC's overlap Address bus and Data bus pins to minimize the number of pins needed. That means one pin can be used as an address pin or as a data pin depending on the current state of the bus. For the logic to work properly address value should be present for the whole read or write operation. To accomplish this the mentioned IC has latches (memory registers) inside. ALE signal stores the pins' state into internal address registers (latches) of this IC. After that the bus can be switched to deliver data on these same pins, that used to carry the address a moment ago.