Obligate carnivore, in plain words
Cats need a diet rich in high-quality animal fats and proteins, plus specific amino acids like taurine that are not found in dog food or human food (Merck). Taurine deficiency causes blindness and heart failure over time — this is why "can I just feed my cat dog food?" has a hard no for an answer.
The AAFCO statement is the first filter
Look for a food labeled "complete and balanced" per AAFCO standards. Merck notes that foods which do not meet the standards must be labeled only as treats or for occasional/supplemental feeding — that label line tells you what the food actually is, regardless of marketing.
Wet vs dry vs mixed
Wet food increases water intake — useful for urinary health; dry food is convenient and cheaper per calorie. Many vets recommend at least partial wet feeding, especially for males and seniors prone to urinary issues. The best food is a complete-and-balanced one your cat eats consistently.
Homemade diets: do not DIY the recipe
Merck is direct: if you're considering a homemade diet, you should not formulate it on your own. Nutrient imbalances in cats develop silently and are expensive to reverse. Use a board-certified veterinary nutritionist if homemade is a must.
Water is part of the diet
Cats have a naturally low thirst drive. Multiple water stations away from the food bowl, wide bowls (whisker-friendly) and fountains all measurably increase intake — and higher intake is protective for kidneys and the urinary tract (Merck kidney guidance).