rendered – Boolean value (if it is true, it displays the block else it will be hidden)

Example – https://infallibletechie.com/2014/02/conditional-rendered-with-list-size.html

reRender – ID. The particular block will be refreshed.

Example – https://infallibletechie.com/2013/04/how-to-rerender-multiple-sections-in.html

renderAs – Display the page as pdf, excel, etc…

Example –https://infallibletechie.com/2012/01/redering-as-pdf-visualforce-page.html

Cheers!!!