colubrids are kind of anything that ISNT a boa, python, or viper. Colubrid is a catch-all group for the 'other snakes'. Kings, corns, garters, milk snakes, bull snakes, gopher snakes, green snakes, etc are all colubrids. They tend to have lighter bodies and smaller heads than boas and pythons, and are more tolerant of lower humidities in most cases.
They are also my favorite group of snakes
(the above description is really simplified, you can do your own research about what truly makes a snake a colubrid vs some other family)