"Hello and welcome!"
Translation:Terve ja tervetuloa!
Its nominative form (dictionary form) is tulo and it means "arrival" in this context, although you rarely see that word in the nominative singular form. In tervetuloa, it is in the partitive singular. terve means "healthy", so you are wishing good health to your guest. :)
Well, they are not the same ("terve" is used as a greeting just like "hei", "moi" etc. are), but while you can use them like this, I'd personally say "Hei, tervetuloa" or "Moi, tervetuloa" just to avoid the feeling of repetition. I think they have included "terve ja tervetuloa" here just to show how these words differ and function.
Interesting! Just to test I put "Moi ja tervetuloa" and it was accepted. Do Finns say "Terve" any more? When I first visited Finland in 1961 "Hei" was the normal Hello for my girlfriend (later wife) and her friends, but now, watching Sorjonen and Karppi on Netflix it seems that "Moi" is the norm.
It so happens that I typed "tervetuola" too, and I got marked correct with a typo. (I have been transposing letters a lot toady.) I suspect hei is not accepted because it's regarded as less formal, but those boundaries don't translate well, so if I see this question in the future I will suggest hei as an alternate, if it isn't already accepted.