On your Safari menu bar, click on History and at the very bottom it says "Clear History..."
Click on that and you will be prompted with an "are you sure" message. If you are sure, click ok to delete your browsing history.
Oops... Forgot part 2 of your question...
The left side column show you the categories, and the right side shows you the actual bookmarks in those categories.
If you remove a category from the left, you lose everything within it (from the right). Think of the left side as being a file cabinet for bookmarks...
So under "Collections", you have History, Bookmarks Bar (this is the row of links below the address line in Safari), Bookmarks Menu, RSS Feeds, and below that are Bookmark groups (where you can add or remove folders to organize bookmarks of a specific type).
If you want to just delete individual bookmarks, do this on the right side ONLY. Pick the bookmark location (from the left), and then on the right side of the screen, right-click on the bookmark you no longer want and click the "delete" option (that will appear in a small options box).
If you want to remove a bookmark from the bar (below the address line of Safari), you can follow the steps to delete individual bookmarks, or just click and drag the bookmark off the bar and a "poof" cloud shows you that its been removed.
I hope that helps.
Message was edited by: canucksgirl01