The same class of Drivers

The average driver with just a few violations spread over many years would be classified as a standard risk. This person also has  a car that is not extremely expensive or statistically at high risk of accidents and this is the class of drivers that most insurance companies will insure.
The characteristics that statistically are correlated with low risk of accidents are the ones with outstanding driving records, so there are a few companies that concentrate on attracting these drivers. Preferred is the name given to these drivers. Companies that insure basically the preferred driver will expect to see a lower than average incidence of accidents and will then be able to charge lower premiums to them.
On the other side of the fence, is the non-standard risks. These are the drivers who, through their own history of driving, are a higher risk because of having accidents. There is also those companies that will cover a broad range of drivers where others will insure just one segment. Some get a fleet of companies, each with different underwriting goals. Then there are those who do not fit in any category. They will then need to get an assigned risk program, which will come at a high price.