The input device captures the handwriting data, that, once digitized, can be displayed on a screen.
These pens emit a weak electrical signal that is detected by the device's touchscreen digitizer.
Camera-based pens use special digital paper to detect where the stylus contacts the writing surface, such as those using NeoLAB or/and Anoto technology.
Digital pens typically contain internal electronics and have features such as touch sensitivity, input buttons, memory for storing handwriting data and transmission capabilities.
A good pen can make a huge difference in the precision and ease of use when interacting with a smartphone, especially for those who find it difficult to navigate the small touchscreen with their fingers.