Orc is the anglicised version of the
Sindarin word yrch, the servants of the
Ainur Melkor. They were most likely created by the perversion of
Elves,
Melkor being unable to
create anything of his own. As such, they shared the immortality of the
Elves, but not their appearance. Black, sallow, and stunted, most preferred darkness, however breeds such as the Uruk-Hai were able to endure sunlight.
Tolkien referred to the Orcs as
Goblins in
The Hobbit, but they're the same thing.