Yet another great option for giving your users extra information with minimal effort are tooltips and popovers.  With these two features, users can hover/click some text or photos and get additional relevant information without having to leave the page.

Tooltips (hover) give you a small space to place data, while Popovers (need to click) give you more.

These components are useful for things like definitions, help in filling out a form, and for providing short descriptions that would otherwise clutter the page.