With the Android app, pinning a photo from the Web is simple, thanks to Android's Share function. From any browser, just go to Android's built-in share menu, and choose "create pin." From here, you can choose which photo to pin, select a pinboard, add a description, and so on. The workflow here is exactly like that on the Web site. Additionally, you can create a pin directly from the Pinterest app with a photo or by inputting a Web address.
Meanwhile, iOS users cannot create pins directly from the browser since Safari doesn't play well with other apps. The good thing is that with recent updates, you can now navigate to a Web site and create a new pin from within the Pinterest iOS app. Alternatively, you can also try to install the Pinterest bookmarklet to pin something directly from your Safari browser.
From the mobile app, it's also easy to create new boards. As well, for boards that already exist, you can edit board names, descriptions, and categories. You cannot, however, change the cover photo of a board. That you must do on the Web.
With the newest update to the Pinterest mobile app, you can now mention other users in comments and pins. This is great for spurring conversation and directing your friends' attention to something specific. Another addition is the Send tool, which lets you quickly share pins with your friends on Pinterest or with others through e-mail.
In a future update, I'd love to see pinch-to-zoom controls come to the Pinterest app. Since the app constrains the images to the width of your device, it can be hard to see details of smaller photos or those containing small text.
If you fancy yourself an avid pinner, then the Pinterest mobile app rocks. It's a beautiful app that offers an rich experience that is very similar that of the full Web site. It's great for creating boards, pinning items, sharing items, and even editing profile information.