Commonly used to refer to a sign or evidence of something.
El rastro de las huellas en la arena era visible.
The trace of the footprints in the sand was visible.
A medida que caminábamos por la playa, el rastro de nuestras pisadas iba desapareciendo con la marea.
As we walked along the beach, the trace of our footsteps was disappearing with the tide.
Es fundamental que se conserve el rastro de la historia para entender nuestro pasado.
It is essential that the trace of history is preserved to understand our past.