Apple introduced Touch ID fingerprint recognition with the iPhone 5S, it's believed to represent a significant improvement of iPhone users' data protection. In its basic description, Touch ID takes a 550 dpi resolution picture of your fingerprint by the help of a capacitive sensor, then iOS stores a mathematical representation of this image in the Secure Enclave, so technically, no image of your fingerprint is stored either in the device or in Apple's servers (including iCloud).
To match a fingerprint there are two main features of the fingerprint pattern: patterns (Figure 1) and minutia points (Figure 2), as you can see from the following images (images from https://en.wikipedia.org/wiki/Fingerprint_recognition):
Basically, a fingerprint can be created from the difference in electrical conductivity between the epidermal and the dermal (not conductive) layers; this difference...