There are hundreds of food brands for us ; cat food is sold in the supermarket, in specialized stores, or at the veterinarian.
We find wet food, dry food (kibbles), or still semi-wet. Prices can be multiplied by nine between the cheapest and the most expensive product.

In Europe, Nestlé Purina (Félix, Friskies, Gourmet, Vital Balance in supermarket, and Purina in specialized store for example) and Masterfoods (Whiskas, Kitekat, Ronron, Sheba in supermarket, and Royal Canin in specialized store) realizes roughly 2/3 of the sales ; the rest is divided between the own brands of the distributors, Procter and Gamble (Iams), Colgate-Palmolive (Hills), and some rare independent small companies.

How can the humans find themselves there ?

By showing common sense : quality has a price. A wet food containing less than 8 % of meat and ingredients of low quality will be cheap, but won’t have the same nourishing properties as a more expensive food containing at least 25 % of meat developed with good quality ingredients.
By inquiring : veterinarian, specialized literature, specialized web sites. You can give us factory feedstuffs, or prepare us yourself our meals (BARF or cooked dishes); this last option requires however good knowledge in feline nutrition. A cat is a strict carnivore, and his food has to bring to him, in percentage of dry material : 30 to 40 % of proteins, 10 to 15 % of fats, less than 45 % of carbohydrates, as well as several vitamins and key nutriments as taurine and arginine. Wet food will have a bigger proportion of proteins than dry food.
By making the best choice for us : your human has to take into account his budget AND your health ; he must however know that by saving up on the quality of the food, he can maybe find himself with veterinarian’s more important expenses in a few years.

Claire chose to feed us mainly with top-quality wet food ; we just get some kibbles for night, but they’re also top-quality. We’ll explain you in another article why she chose this food brand for us.
In the meantime, here are three books that we recommend you to read about pet food ; we don’t know if there are translations in your human’s language.

In French :
In English :
In German :