Activating the All in one SEO pack provides you with some additional fields to enter when you create/update a page or post. There is a tutorial that you can watch: Tutorial Video for All in one SEO pack
The fields you enter (Title, Description and Keywords) can affect your placement in Google rankings.
The information is of more use to search engines rather than your human site visitors.

WoW Examples

The All in one SEO pack is implemented on each Wonder of WordPress website.

Further reading