Binaural beats are a form of “auditory beat stimulation”, which includes both monaural and binaural beats. They can probably alter the abundance of certain brainwaves, which may improve or alter mental states to make users better at memorization, paying attention, or relaxing.
The beats are formed by playing two tones with slightly different frequencies in unison. A monaural beat is formed when these tones are combined before they are played through a speaker, whereas a binaural beat is formed when each tone is played separately into each ear, producing a perceived third tone that is equal to the difference between the two base tones. For example, an individual may have a 240 Hz tone played in one ear and a 245 Hz tone played in the other, which will produce the illusion of a third 5 Hz tone.
Binaural beats are an auditory illusion produced by playing two slightly different tones into each ear, and are tuned to the frequency of certain brainwaves to produce a desired effect.
Although binaural beats have been studied in diseases such as Parkinson’s, cardiovascular disease,  and tinnitus, the bulk of the research has been dedicated to improving sleep, cognitive factors, and pain. Broadly speaking, binaural beats seem to have modest to strong effects on sleep, memory, attention, mood, and pain.
A quick note about the studies: the “control” groups vary considerably, and include silence, white noise, music, and sham sounds. Developing adequate controls is difficult with a treatment like this, which is worth keeping in mind.
While binaural beats have been investigated for a variety of outcomes, the best evidence lies in their effects on memory, relaxation, and pain.
Lower-frequency binaural beats in the delta, theta, and alpha ranges seem to produce relaxation and pain reduction, and higher frequency beats in the beta and gamma range may be able to improve memory.
Lower-frequency beats may make memory worse acutely, by producing neural states that are incompatible with encoding information.