die Warteschlange
queue / line
A row of people waiting one after another to be served, admitted, or to have their turn.
An der Supermarktkasse bildete sich eine lange Warteschlange.
A long queue formed at the supermarket checkout.

queue / line
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queue / line
A row of people waiting one after another to be served, admitted, or to have their turn.
An der Supermarktkasse bildete sich eine lange Warteschlange.
A long queue formed at the supermarket checkout.

'Warteschlange' (queue/line) is made up of the verb 'warten' (to wait) and the noun 'die Schlange' (the snake/line). It figuratively describes a row of waiting people that looks like a long snake.
Die Warteschlange vor dem Kino war so lang, dass sie um die Ecke ging.
The queue in front of the cinema was so long that it went around the corner.
When you are part of a physical queue, you use the verbs 'stehen' (to stand) or 'sich anstellen' (to line up). You 'steht in der Warteschlange' (stand in the queue) or 'stellt sich in der Warteschlange an' (line up in the queue).
Wir mussten fast eine Stunde in der Warteschlange stehen.
We had to stand in the queue for almost an hour.
You can recognize the second meaning from signal words like 'digital' (digital), 'virtuell' (virtual), 'online' (online), or in contexts such as telephone hotlines or websites. Here you are not waiting physically, but in a system.
Ihre Anfrage befindet sich in der digitalen Warteschlange und wird bald bearbeitet.
Your request is in the digital queue and will be processed soon.
row / series
'die Reihe' and 'die Warteschlange' can both mean several people standing one after another. 'die Reihe' only describes the order or line. The people or things do not have to be waiting. 'die Warteschlange' is used when people are waiting to be served or allowed in. That is why you can stand 'in einer Reihe' (in a line) at a checkout, but more precisely you would say 'in der Warteschlange' (in the queue / line). The risk of confusion comes from the fact that a queue often looks like a row.

Vor dem Schalter steht am Montag eine lange Warteschlange.
On Monday, there is a long queue in front of the counter.
Am Abend stellen sie die Stühle in eine lange Reihe.
In the evening, they put the chairs in a long row.