In brief
animation-direction controls forward, reverse or alternating playback. alternate can move forward and backward across successive cycles.
Useful to know
animation-direction controls forward, reverse or alternating playback. alternate can move forward and backward across successive cycles. [1]
For a swaying detail, this avoids a separate reverse animation. Direction does not set iteration count, however: with only one iteration, do not expect an automatic return during a subsequent cycle.
Sources
For further detail and to check the information: