Animation Notifications provide a way for to let events to occur at specific points during an Animation Sequence.
There are a few built in notifies.
Clothing Simulation: Pause Clothing Simulation, Resume Clothing Simulation and Reset Clothing Simulation.
Play Particle Effect: Spawn and play a particle system at a given socket location.
Skeleton Notifies (AN_)
Lets you place a named notify at points in an animation track and then get it called as an event in the animation blueprint of the skeletal mesh.
Anim Notify States (ANS_)
With this you can create a notify state blueprint and activate it over a range of time in an animation track. The event graph of the blueprint will have 3 events, begin, tick and end.