A species is a kind of organism. It is a basic unit of biological classification, and a formal rank in taxonomy. Originally, the word was used informally in a rather vague way, but now there are at least 26 different ways it is used.
All animals or plants that are the same kind belong to the same species. Wolves (Canis lupus) are one species. Humans (Homo sapiens) are another species. Broadly, the idea is that, for example, cats breed with cats and produce more cats. This is the basis for deciding to have a species called Felis catus. However, to give a simple definition of 'species' is difficult, and many people have tried.
Species is a word for a particular kind of living thing, for example, a jackdaw. Jackdaws and ravens are similar, so they are together in a larger group (taxon) called a genus, in this case Corvus. Then there is a family (such as the crow family, which includes crows and ravens as well as jays and magpies). Families are put together into orders such as the songbirds, which includes many families of birds. The next group is the class; all birds are in the same class. After that is the phylum, such as vertebrates, which is all animals with backbones. Last of all is the kingdom, like the animal kingdom. These are ways to classify living things.
There is a mnemonic to help people remember the order of the divisions which are listed again below: "King Phillip Came Over For Great Spaghetti".