Hi Mike. Expand means to stretch or to increase in size or bulk. For example a thin woman might say, 'I want my waist to expand to 3 more cms so that my new dress will fit just right'. Another woman might say,' I don't want my waist to expand by 3cms because I won't fit into my new dress.'

Expand to - whatever is "expanded to" is being reached. Example - the audience was expanded to include teenagers - so the teenage audience is being reached expand by - how much something is going to be expanded, or how they are going to expand example - their cookie production has expanded by 2/3 since the beginning of the year! Or they are going to expand their market by giving out free samples. I hope this helps. <(^_^)>