It may not look like it, but the iTunes Store is simply a bunch of web pages rendered in the iTunes application. Using WebKit, the HTML rendering framework that is used by Safari, Mail and many other Mac applications, iTunes displays the iTunes Store in its window simply by displaying the content from web pages.
These web pages have standard URLs, but you can’t save bookmarks in iTunes. You can, however, copy links to any iTunes Store pages by right-clicking on an item, then selecting Copy Link. For example, here’s a link to a recently released live album by the Jerry Garcia Band: https://itunes.apple.com/us/album/garcialive-vol.-two-august/id652516671 You can see that this is a standard web URL. If you click on the link, you’ll be taken to a web page in your browser, which will either display in your browser or launch the iTunes Store to the appropriate page. (It’s not clear why some URLs open the iTunes Store and others don’t.) If you want, you can save this URL as a bookmark in your web browser, or you can send it to a friend.
By the way, let me mention an excellent Safari extension: NoMoreiTunes prevents Safari from redirecting to the iTunes Store, so if you click on a link or paste a URL into Safari’s address bar, you can view the content in the browser rather than bouncing to the iTunes Store. If you decide that you do want to view a page in the iTunes Store, just click on the Open in iTunes button. This is a good way to view pages then easily save them as bookmarks.