If you mean "queue", that means put in line for production/research/etc.
Just like standing in line at a movie theater, that's a queue
If you want a code monkey term, it's a FIFO queue (First In First Out) as opposed to LIFO (Last In First Out)
Anyway, in terms of the game it means it will be build/researched/attacked/etc when its turn comes.
Hope that helps
