side
The word 'lato' in Italian is used to refer to a surface or aspect, typically of a structure or feature, either literal as in the side of a building ('il lato dell'edificio'), or metaphorical as in side of a story ('il lato della storia').
The book is on the left side of the table
This phrase is used to describe the location of objects, by using the word 'lato' (side) combined with orientation (sinistro/left), it indicates where the book is located.
We are going towards the opposite side
In this context, ‘lato’ is used to signify a direction or destination. The add-on word ‘opposto’ (opposite) gives further specification to which side the subject (we) is moving towards.
The sweet side of life
This is an idiomatic expression. When used in this context, 'lato' refers to an aspect or part of something. Here it infers to the pleasant aspects or moments of life.