The main difference between reciprocating and rotary air compressors is how the air is compressed.
Reciprocating air compressors use pistons pumping up and down to compress the air within the cylinder chamber of the pump. Reciprocating units are best suited for commercial businesses, workshops, home use, construction sites, etc. (See figure A)
A rotary air compressor (or screw unit) uses a set of spinning, helical screws to compress the air and pressurize it. Rotary units are designed to provide constant air and are best suited for industrial and commercial applications. They do run cooler and quieter than reciprocating compressors and have fewer moving parts. (See figure B)