It can be used in many different contexts, for example:
* "El lado derecho" - the right side
* "El lado izquierdo" - the left side
* "El lado oscuro" - the dark side
* "El lado positivo" - the positive side
* "El lado de la calle" - the side of the street
Important note: "Lado" is masculine, so you would use "el" in front of it.