To view the site content and structure page, go to Site Actions > Site Settings and look for Content and structure under the Site Administration section. The site collection must have the Publishing feature (SharePoint Server Publishing Infrastructure) enabled for you to be able to get to the site content and structure page.
You can see the site collection hierarchy in the Navigation Pane on the left. The List Pane on the right is where content is shown.
One of the useful things you can do in the site content and structure page is to work with multiple items. In this screen shot, I am moving multiple documents. Start by checking (click the check boxes of) the items you want to move (same applies if you want to copy, delete, check out, discard check out, or check in items). When moving items, click the Actions drop-down menu, and click Move.
You'll then get a dialog box that pops up telling you to specify the destination to move the items you selected. Click the list or library you want to move the items to, then click OK. You'll then be sent to a page that gives you status information about the move taking place.
By default, the list pane is limited to showing 100 items. You can change this by clicking the Show menu on the far right. Beware that moving or doing other work with many items (e.g., 100's at a time) can take some time, just as moving files around on your PC can take time.
You'll also want to explore the other items on the menu. For example, you can create new items, get to list settings, add items to your favorites, and change views.
The View dropdown menu is particularly useful for seeing items checked out to you, modified by you, pending approval, and so on.
If you don't see Content and structure under the Site Administration section and would like to work with this feature, please check that the Publishing feature is enabled. If you don't have this enable and cannot, or don't know how to enable it, reach out to your SharePoint site collection or farm admins.