The key beliefs of Jainism are that the way to achieve freedom and liberation of the soul is to live a life characterised by peace and sacrifice. In addition, there is a massive emphasis placed on caring for all living forms of life, including the universe itself. For example, Jainism states that all living creatures have their own souls, just like humans, and that these souls are equal. Therefore, each living creature must be treated in the same way as humans. This is why Jainists are vegetarians, and believe in eating and living in such a way as to minimise the world's resources. Often Jainists are famous for wearing veils across their face in case they inadvertently kill a fly or some other insect. Note, for example, the following quote said by Yogashastra in Jainist scripture:
In happiness and suffering, in joy and grief, we should regard all creatures as we regard our own self, and should therefore refrain from inflicting upon others such injury as would appear undesirable to us if inflicted upon ourselves.
This indicates the high value placed on preserving all life, no matter how small that life may be. As a religion that evolved out of Hinduism, there are many similarities, such as the belief in reincarnation and the end goal of freeing oneself from karma and becoming enlightened. However, Jainists believe that there are no gods that help humans in their quest for enlightenment, and also that Jainists should be complete pacificists. The "three jewels" of Jainism are right belief, right knowledge and right conduct. It is the focus on the preservation of human life however that clearly separates Jainism from Buddhism and Hinduism.
Though all three belief systems effectively practice non-violence towards other organisms and preach that the negative effects on the karmic cycle can be greatly reduced by minimizing consumption of meat (it is believed that every living thing has its own karma, and hence, by eating an animal, our karmic cycle takes on the burden of those beings), Jainism also practices non-consumption of all foods after sunset (because that's when the system is shutting down for a night's rest), as well as abstinence from foods that are intoxicating or bring about unwanted changes in our systems. The Jain diet is mostly restricted to 'satvik' foods - foods that do not adversely affect either physiological or emotional faculties. For example, no alcohol, no onions/garlic, no aphrodisiacs, no mood-altering foods, etc.
I hope this helps!