Living organisms are living objects made from protein and other organic material, their study is called Biology. The protein is made from a sequence of amino acid, which is determined by DNA.
Living organisms on Earth almost always consist of cells with a nucleus and cytoplasm but there are some organic structures like viruses which are not clearly living or non-living.
Christians believe that humans are superior organisms, because they are the smartest and the bible says they are made in god's image. However humans could easily evolve into another organism which is even smarter.
Hindus believe that animals are good organisms, because they have a nervous system. However, many animals don't have a nervous system.
Living organisms developed out of non-living material, see Abiogenesis.