Antibiotics fight bacteria. This isn’t a science meme.

While some fungi do make antifungal compounds (like 95 % sure, I may be wrong) that work against other fungi, potentially. Antibiotics are specifically for bacteria.

Antibiotics kill (some) bacteria and are ineffective against viruses, fungi, protists and depending on the class, certain types of bacteria.

Fungicides kill fungi.

Penicillin for example, kills gram positive bacteria by disrupting their ability to make sturdy cell walls. Weak cell walls aren’t stromg enough to maintain the integrity of the cell against the osmotic pressure that is trying to pop them like a balloon so they… pop like a balloon (lyse)