Small Single Engine airplanes are most commonly "trainer" airplanes models could include Cessna 152/172, Piper Archer, and a Cirrus SR20. Comon characteristics are 4 cylinders, compact fuselage, and fixed gear. 

Large Single Engine airplanes are most commonly endorsment planes. Models could include Cirrus SR22, Beechcraft Bonanza, and Cessna 182. Typically require high performance or complex endorsments. 

*This excludes tailwheel endorsment.