In what form do food interactions of organisms manifest themselves?

Living organisms are in different relationships with each other due to different digestion. For example – there is predation. Predators cannot digest plant foods, so they need an intermediary – a herbivore. So predators that eat herbivores are first-order consumers. If a predator eats another predator, then he is a consumer of the second order. There can be symbiosis between organisms. So they get mutual benefit. For example, a symbiosis of fungi and unicellular algae.