Allow the action you need
An app that reads or changes a page needs permission for that capability and website. Power shows the request outside the app. Review the action and site before allowing it. Chrome's website access and an app's permission are separate controls.
Access for one website does not grant access to other websites. Remembered permission can be used again on a permitted site, but Power still checks the current tab and page for each action.
All websites
For a tool you want to use across sites, All websites covers HTTP and HTTPS websites, including future sites, until you revoke it. Each app still needs its own permission. Chrome's internal pages and other browser-protected pages remain restricted.
Stop or revoke access
Use Settings → Website and app access to review Chrome access and App permissions. Turning broad website access off stops that access; sites separately allowed in Chrome may remain. Revoking app permission keeps the app and its saved data, but stops the affected capability.
Use Stop for a running task. Stop prevents further steps; it cannot undo an action already completed on a website. Closing an app view alone is not a way to revoke permission.