There’s a joke that the word queue is just the letter Q with four silent letters queued up after it, which gives you a hint at its meaning, if you don’t know. A queue is a line, either in-person or online. We don’t use it much in the US; this is used more in British English. 

It came to English from French, which explains all the silent letters, and originally meant ‘tail’. (1) It used to be used for a man’s hair tied back in a tail as well. By the way, it’s just pronounced like the letter Q.

Queue can be used as a noun: I joined the queue to buy tickets for the show. 

Or as a verb: I queued up to buy tickets for the show.

Queue is often mixed up with the word cue, which is a homophone (a word that sounds the same but is spelled differently and has a different meaning). The spelling of queue can be confusing, so the difficulty is understandable. 

Cue has a couple of different meanings. It can mean a hint or a signal: He cued me to start my speech. 

A cue is also the stick used to play pool: I picked up my cue and prepared to take my shot.

While queue is not used often in American English, it is wise to learn the difference, so you can recognize it and use it correctly. 

(1) https://www.etymonline.com/word/queue