The Common Web Platform 2.0 comes with two themes that help government agencies get their sites up and running quickly.
The CWP Starter theme(external link) is a developer focused highly accessible(external link) Bootstrap 3 theme that is suited for sites that require more customisation and design. The theme can be applied with minimal restrictions and is intended more as a starting point for customisation in order to speed up development.
The Wātea theme(external link), on the other hand, includes more design elements than the CWP Starter theme and so is more fully featured as a quick 'up and running' option, particularly suited to short-term campaign sites or sites which needs a decent starting point which will be added to as time goes on. Out of interest, the Wātea theme currently powers cwp.govt.nz (this site) with some minor changes. Wātea is well suited for smaller agencies with smaller sites, smaller budgets and smaller developer teams. This Wātea theme is a sub-theme of the Starter theme. It provides a more visually appealing layer to jump start projects.
The CWP Agency Extensions Module(external link) provides added configuration and underlying functionality that may be useful to allow clients/agencies to adjust website functionality themselves. It provides the content management side of the functionality provided by the Wātea theme (specifically Wātea Plus which adjusts site fonts and colours and the Carousel).
Please note CWP also has a legacy theme which might still be used by some agencies on CWP 1.0 called the Default theme(external link), there could still be references to this theme throughout these guides and documentation for CWP.