As far as I know, they are different. A goblin is an evil or merely mischievous creature of folklore, often described as a grotesquely disfigured or elf-like phantom. An orc is one of a race of mythical human-like creatures, generally described as fierce and combative, with grotesque features and often black, grey or greenish skin. Orcs are generally seen as repulsive and are sometimes thought to not be able to handle direct sunlight just as many other monsters were in history as to show that people could not be harmed by them in sunlight. The thing is as far as I can recall, they were really not described in length in the books. It was just our imagination at work when we read the books.