欢迎光临 (huānyíng guānglín) is the traditional formal welomce in Chinese. You can hear it spoken when entering a shop, restaurant or hotel and you will see it written on signs, printed on foot mats or displayed on red welcoming banners at official events.
欢迎 simple means welcome (literally, happy welcome). 光临 means to be present or presence. It is mainly used in formal situations and is most common as part of the fixed expression 欢迎光临.
Note that many fixed expressions in Chinese consist of four characters, while most words are only one or two characters long.