These are just a few of the terms that may be helpful for you to understand when choosing which one of the many electric air compressors may be best for you. Also, make sure the tank size will support the type of jobs you will be doing. My husband is disappointed (yea,right!) that his 4 gallon tank, that he has owned for years, is not large enough to operate a sprayer, so he may have to purchase a larger one to get the job done right!