how can i tell? what does it look like when a cat has an ear infection?

basically, since yesterday, he has been walking with his head slightly tilted to the left & he is keeping his left ear slightly pointed down -- at first, i thought he hurt his neck, but then i read about it online and it said if a cat has a neck injury, he wouldnt be jumping or walking up and down the stairs.... and miller has been fine otherwise

so anyways, then i thought it was an ear infection so i was wondering if anyone had any insight in this area lol