how to use the word "welcome" / “welcome"的三用法
如何使用“欢迎”/“欢迎”的三种用法

(1) "to be welcome + infinitive" - This is invitation to do something  这是邀请（某人）做某事


example: "you're welcome to come visit my country any time", "you are welcome to join us for dinner tonight"
例如：“随时欢迎你（阁下）访问我的国家”；“欢迎你今晚与我们共进晚餐！”
(2) "you're welcome" - a response to "thank you"  作为谢谢的回复

"Thanks!" "You're welcome!"
谢谢！不客气！
I suppose the meaning is really something like "you are welcome (to my help)".
我想这个意思是“我很高兴能帮上你。”（这句直译不出来。）
(3) "welcome to ___" - said the first time you see someone who has recently arrived. 欢迎来到。。，客人初驾到时的首次见面

Usually on a sign when someone arrives, or said when they get off a plane.
往往是某人刚来或即将登机离去。