Learn in the textbookFundamentals of Interface Design and Input Operations
DefinitionTap (タップ) is the most basic touch gesture: lightly touching one point on a touch screen with a finger and lifting it right away.
ExplanationIt corresponds to a mouse click and is used to select or run icons and buttons. There are also variations that change how you touch, such as a double tap (ダブルタップ), two quick light touches on the same spot.
AnalogyIt is close to pressing an elevator's floor button lightly with a fingertip. A touch and a release are enough to select and confirm.
Memory hookThe English word tap means to strike lightly. Picture tapping someone on the shoulder to get their attention.