1. （连接两个或两个以上选择的可能性）或，或者，还是
You use or to link two or more alternatives.
e.g. 'Tea or coffee?' John asked...
“喝茶还是喝咖啡？”约翰问道。
e.g. Was she blonde or brunette?...
她的头发是金色还是深褐色？
2. （与 either 或 whether 连用，给出另一个选择项）或，还是，就是
You use or to give another alternative, when the first alternative is introduced by 'either' or 'whether'.
e.g. Items like bread, milk and meat were either unavailable or could be obtained only on the black market...
像面包、牛奶和肉之类的东西要么是买不到，要么就是只能去黑市买。
e.g. Either you can talk to him, or I will...
要么你跟他谈，要么我去。