Clarity on the Italian Game opening?

I'm watching the learning videos and Bishop to f4 is one of the recommended moves via the Italian Game opening because f4 puts pressure on a weak f7 square. But I don't understand why f7 is weak since the King is there to guard it. Is it because Black should not consider their king as a defending piece?

There's no immediate threat, because, as you say, the square is guarded by the king. But if White can reinforce that attack with another piece, such as a knight on g5, the pawn will be in danger - this happens in some lines and leads to various tactical motifs. But the main point is to put your bishoop on a good active square where such possibilities may arrive in the future. It's not the only good move in the position, but it's one of the best.

f7/f2 is widely considered to be the weakest square on the board for two reasons.
Firstly, because if you attack it with two pieces, the king can be checkmated very easily, leading to incredibly short games sometimes.
Secondly, if you push that pawn, suddenly bishops and queens have access to the diagonal, leading to even more early checkmates.
The reason this weakness isn't all-consuming is because Nf6/Nf3 exists to deny Qh5/Qh4 and Qf3/Qf6. In the Italian Game, this is known as the Two Knights Defense and is the best way to continue as Black. The most solid continuation against the Knight Attack, which leads to the Fried Liver, is to play the following:

This is the Polerio Defense, where although Black is down a pawn and has a relatively shattered queenside, it's going to take a long time for White to be able to properly develop, as there are three pieces between the rooks, the bishop isn't getting out any time soon, and those doubled IQPs are going to be a problem. 0.0 down a pawn is a pretty good position.

Yes, it is because you should not consider the king to be a defending piece. It is not a good defender. Always keep on the lookout for Bxf7 ideas.

augh

Bishop to f4 is not one of the moves of the Italian Game Bf4 is THE move that defines the game as the Italian.

c4.

Bishop goes to c4, not f4.

The f7 square is weak becuse it's only protected by the king, and the king should NEVER be a defender (minus endgames)

It shouldn't be, just click the button right above your comment that looks like a miniature chess board and click 'Load from URL'.