He wrote many scaryshort stories. These often were about weird creatures that Lovecraft made up by himself or with his friend, August Derleth, who wrote mysteries. The creatures did not really care about human people at all, so they were not out to hurt people, but if they did, they did not care. They looked at us like we would be ants. Their behaviour, attitude and look also tended to make people go crazy.
Lovecraft's stories were inspiration for lots of other authors.