To enqueue something means to add it to a queue, where it can wait until it is handled. A queue is like a line, so a new item often joins behind the others already waiting.
For example, when you send several photos to print, the computer may put each one in a queue so they are printed in turn.
Enqueueing a task usually means it has been accepted into the waiting line, not that the work is already finished. The app may need to tell you when it starts and when it is complete.