is it after someone says "thank you" and you stay "you are welcome" or is it in the sense of "welcome in the shop" ?
"Welcome to the shop" or if you turn on your Korean computer, "welcome to your computer"
I guess they accept "You are welcome" in the sense of "i am welcoming you in my shop / you are welcome to come into my shop" ? and not the thank you/you're welcome dynamic ?
환영 sounds so similar to the Mandarin pronunciation of its Hanja 歡迎 (huānyíng) :)
The first one is more like a text book formal, the latter is the casual formal.