I wonder what tag should this sentence have.

Well, maybe Cookie Clicker grandmas are. They are quite good at it, at any rate.

"pwn" and "noob" are slang used on the internet and in video games.
I explained the terms in the comment section of the Dutch sentence (Dutch internet slang is heavily influenced by English internet slang), and I thought I might as well share the same information here.

"noob" (often spelled "n00b") comes from the word "newbie", and is a (usually derogatory) word for someone who is inexperienced or incompetent. It's mainly used in online videogames for players who are bad at the game.
For example:
- "He just blew himself up with his own bazooka! What a noob!"
("what a noob" has the same kind of feel to it as "what an idiot" and "what a moron", but has a lot more to do with skill and competence than with intelligence)

"pwn" was originally a typo of "own", which people later started using on purpose.
"To own" was originally an expression for when a computer hacker managed to gain complete access to the computer of someone else (and thus "own" the computer). Later people started figuratively using the term in video games for thoroughly defeating an opponent, after which it seeped its way into general slang.
By "owning" or "pwning" people usually mean "to be much better than someone" or "to wipe the floor with someone" or "to humiliate someone"
For example:
- "They completely owned me" (meaning: "they utterly defeated me" or "they completely humiliated me")

So "to pwn noobs" is slang for "to sweep the floor with incompetent people", or a bit less literally: "to utterly defeat everyone in as much that it's clear as day that you are much better and more competent than the rest". The expression is mainly used in competitive videogames that are played over the internet.