Too Long; Didn't Read
According to LEO Digital Marketing:
A/B Split Testing takes the guesswork out of optimization by giving you hard data on what drives results. It allows you to test 2 different methods to see which performs best.
According to Wikipedia:
A/B testing is a shorthand for a simple randomized controlled experiment, in which two samples (A and B) of a single vector-variable are compared.
These values are similar except for one variation which might affect a user's behavior. A/B tests are widely considered the simplest form of controlled experiment. However, by adding more variants to the test, its complexity grows.