In Star Trek, what technology hides a vessel from normal visual and sensor detection?

In Star Trek, a cloaking device hides a vessel from normal visual and sensor detection.

A cloaking device bends, redirects, or otherwise manipulates energy and information around a ship so that outside observers cannot easily detect it. The technology is most strongly associated with the Romulan Star Empire and the Klingon Empire. Cloaked vessels can approach targets, conduct reconnaissance, or attack with an element of surprise.

A cloak is not simply a dark paint scheme or a holographic picture. It affects how sensors perceive the vessel, although different stories show different limitations. Some cloaks require the ship to reduce or stop weapons use, while advanced forms can conceal a vessel under more demanding conditions.

Star Trek also distinguishes ordinary cloaking devices from special technologies such as the phase cloak introduced in Star Trek: The Next Generation. The phase cloak was experimental and could let a ship pass through matter in the episode “The Pegasus.” That unusual device is not the standard cloak used by Klingon and Romulan ships.