As with people, gnomes have a wide range of personalities and emotions which can lead to some of them considered good and others bad. However, in general, they are considered to be good (as well lucky!) creatures and which humans should be happy to have around them. This is why so may people keep them in their homes and gardens.
The good side of gnomes is what most people know them for (we have an article dedicated to their entire history here) and they will do things such as tend to the gardens of humans to ensure that the grass, plants and everything else there is taken care of even to the point of protecting things such as minerals and gold. They are social creatures and the good side of them means that they care for the other gnomes in their community by helping them when they are sick, finding food via activities such as fishing and going out to get wood for their fires to keep each other warm.
As mentioned earlier in this article, gnomes can also be bad. This is usually do to them being scared and so they feel that the need to protect themselves and their community. This can involve them biting whatever is causing them to feel such stress and to get away from it.
In general though, throughout the years in mythology gnomes have been considered to be quite neutral. Their have often appeared in the background of stories with not too much said about them and in modern stories, such as the Harry Potter books and movies, they have been considered to be something of a pest but nothing too extreme.