After receiving your private pilot certificate, you may choose to pursue training towards a high performance or complex endorsement. An endorsement is a one-time sign off by a certified flight instructor and unlike a certificate, there is no checkride required.

FAA definitions as defined by §61.31 :

Complex: An aircraft equipped with a retractable landing gear, controllable pitch prop and flaps

High Performance: An aircraft with an engine of more than 200 horsepower

10 hours of complex training or technically advanced training is required for a commercial pilot certificate.