The word backward is typically used as an adjective that refers to a direction or movement towards the back or in reverse. It may also describe a regression in development or progression. The term is most appropriately used in contexts which require a descriptive word to characterize a state or condition, rather than the act of moving itself.

Used primarily as an adverb, backwards refers to the action of moving in the reverse direction, often away from a starting point or goal. It suggests literal physical movement as well as metaphorical contexts implying retreat or regression. Backwards is the form you'll most likely encounter in discussions about the way a situation, object, or person is moving or oriented.

To summarize, backward is an adjective that characterizes something as reverse or regressive, whereas backwards is primarily used as an adverb to describe a motion done in reverse. The choice between the two often comes down to the function within the sentence: if you're describing a state, use backward; if you're describing an action, go with backwards. Remember to keep in mind regional preferences; American English favors 'backward,' while backwards is more commonly used in British English.