Open a bookmarks sidebar by clicking on the blue button (CTRL+B):
which will open a sidebar on the left, allowing you to view your tags (in the upper half) and your bookmarks (in the lower half):
Notice how moving your mouse over the yellow sticky note icon in the lower pane will bring up a small box with any notes you saved with the bookmark.
Useful if you want to remember in more detail the site you bookmarked.