A target area in a website or app is an area that enables a user to interact with the interface through touch or a pointing device such as a mouse.
Examples are links, buttons, form elements, etc.
According to Fitts’s law, “the time required to rapidly move to a target area is a function of the ratio between the distance to the target and the width of the target”.
For a target area to be easily tapped or clicked by the user, its area must be adequate enough to be interacted upon.
Visually, it may appear small (such as an icon), however, it could still have an adequate target area.