Food gives tortoises the energy they need to get around and do tortoise-y stuff, and also the nutritional building blocks they need to grow bigger and stay healthy... it's important to give them what they need.
The care guides provided elsewhere on this site give you the general outline of what the different types of tortoises need in terms of food, but there are a few things worth breaking out a bit more when discussing tortoise diets
Omnivores versus Herbivores
Basically, some tortoises, generally the forest species, are omnivorous, meaning they can eat some of lots of different foods, including animal protein (meat) and some fruits; other tortoises, generally the grassland or desert species, are herbivorous, restricted to eating plant matter, and beyond that, restricted to mostly grasses and greens and the occasional low-starch veggies.
- hibiscus flowers