Drawing From Reference

'When we talk about drawing from reference, we are talking about having some source of visual information to inform your drawing' 

For example if i want to draw the Eiffel tower, I need to look at its photograph because I can't remember  exactly what it looks like on top of my head. 

'Illustrators and artists have always collected visual information that informs their own practice'

Well, I did collect some materials that I think might be useful for me e.g. a straw, leaves and a sponge. Visual information does not have to be only illustration, it could be a photograph, favourite artist and interest.