I have been reading through the documentation but something is still not clear to me. If I want to build a template using bootstrap can I just use the core Boostrap ? Thanks
In your theme page_theme.php you can require the core Bootstrap 3 CSS using $this->requireAsset('css', 'bootstrap'). This will load app.css in your theme. Bootstrap is included in app.css along with what appears to be the CSS for the entire concrete5 interface. You couldn't use the Bootstrap CSS if you wanted to because it is scoped to .ccm-ui.