An overlay keyboard is a unique type of keyboard that does not have any pre-defined keys. Instead, numerous functions can be assigned to each button based on the user's preference. This makes overlay keyboards extremely versatile and adaptable to various usage scenarios.

Typically, overlay keyboards consist of a flat grid of keys without labels. Once the keyboard has been programmed, a document referred to as an overlay is placed over each button to label it.

The overlay can be modified to include any combination of text, symbols, and images, making it simpler for users to comprehend the functions associated with each button.

The two-button overlay keyboard is one of the most common types of overlay keyboards, and it is frequently used as a quick and easy means of data entry. This form of keyboard is utilized in numerous industries, including the healthcare, manufacturing, and logistics sectors.