または is a formal conjunction meaning "or" that presents two or more alternatives or choices. It is used to connect nouns, noun phrases, or even entire sentences, and indicates that either option is possible.
When placed between two nouns or noun phrases, または offers a choice between them.
または can also appear at the beginning of a second sentence to present an alternative action or idea.
または is relatively formal and is commonly found in written language, official documents, announcements, forms, and instructions. In casual conversation, speakers typically use か between nouns or それとも between sentences to express "or."
Compare the more casual version: こうひいコーヒーかこうちゃ紅茶、どっちがいいきごう? ("Coffee or tea, which do you want?")
You can chain または to list more than two options, though in practice it is most common with just two.