Short length drill bits (also called stub or screw-machine length) are the shortest and stiffest bits, helping to reduce the chance of deflection or breakage when drilling.
Mechanic’s length drill bits (also called maintenance length) are a little shorter than jobber length and less prone to deflection when drilling.
Jobber drill bits are the most common length drill bit. They offer a good comprise of length and reach to work with the widest range of materials and applications.
Long length drill bits (also called taper length) are a little longer than jobber length allowing for deeper holes and longer reach.
Extra long drill bits (also called extension) have extended lengths for drilling deeper holes or greater reach. They are longer than long length.