Connectors come in Compression style or Quick Connect style. The Compression fittings require a nut to secure the tubing to the connector. With Quick Connect fittings, the tubing is inserted directly into the tubing.
Quick connect fittings are also known as John Quest fittings, TiteGrip fittings, Tite Grip fittings, GA Murdock Mur-Lok fittings, Murlok fittings, Anderson Barrows fittings, Speedfit fittings. See details below about how to install quick connect fittings.