"And you" is used in a variety of contexts to mean that whatever the other person said is also true for "you" as well as for "me" or whoever was referred to originally. So here, Sophia says "Nice to meet you." When Lucas says, "And you", he means, "And I also think it is nice to meet you."
You can also say, "And me" or "And Bob" or some other person. Like, Al: "The company gave me a bonus". Bob: "And me", meaning, the company gave me a bonus also. Or, "Sally is annoying". "And Bob", meaning Bob is annoying too.
In most cases you could say, "You, too" instead of "And you". "And you" is somewhat more formal, but both are informal.