<human>:  Explain Einstein’s theory of relativity in simple terms.
<bot>: Einstein's theory of relativity is the idea that space and time are not absolute, but can change and bend depending on the observer's relative motion or the presence of a gravitational field. This means that things like length and speed, which are intrinsic and part of the fabric of reality, are not fixed, but are relative to the observer. In simple terms, observers traveling at different speeds or in different directions will experience time and space differently.