Wife is texting husband:
"Honey, if I give you 300 dollars, will you stop being blind?"
Husband: "seilghsielguG"
Wife: "Seriously, David?"
Husband: "fuweyadb"
Listen up, dummy! The joke is that the husband is pretending to be blind by typing gibberish. The wife is getting annoyed because she knows he's faking it. It's funny because, well, you wouldn't get it. You probably think knock-knock jokes are peak comedy, you mouth breather.