If a question mentions a fact, name or term you'd like to know more about, you can bookmark further information on it (if available). Such information comes in the form of textual information (such as an explanation as to why a particular answer to a question was or wasn't correct) and links to websites (Wikipedia in most cases, with Wiktionary a distant second and other websites being linked to very rarely).
Bookmarks are explained in the initial tutorial every player must complete at least once.
Note: Bookmarks are all about the "info" part of infotainment (a portmanteau of "information" and "entertainment"). They satisfy your curiosity and help you augment your knowledge, but they have no effect whatsoever on your points, levels, duels, ranking positions, achievements, records etc.
Setting a Bookmark
You can set bookmarks on the Post-Solution Screen. The following (partial) screenshot shows the fourth page of the post-solution information area of the Post-Solution Screen following a MatchTwo question about four songs with "white" in the title:
The line at the top says "Bing Crosby" because that name previously appeared on the Answering Interface and the current page of the post-solution information relates to that artist.
The puzzle-piece logo on the left appears if the website that you are being referred to is operated by the Wikimedia Foundation. That applies to the vast majority of post-solution links in Quizcover.
The URL (= web address) is then shown, usually with an ellipsis (three dots) or two.
The blue circular area with the gold star on top is the button to tap on if you wish to bookmark the post-solution information for this question. After you have done so, the button changes it appearance (the star is filled out with a gold color):
Note: If you set a bookmark, it always relates to the entire post-solution information (including all URLs) available for the same question. That's why the button doesn't change its appearance if you swipe to another page.
Accessing Your Bookmarks
In order to look at and open your bookmarks, tap on the Settings & More button on the home screen:
In the Settings & More menu, look for the second section ("Progress & History"), where you find a "Bookmarks" menu item on the left side of the middle row:
The number below "Bookmarks" indicates the number of questions whose post-solution information you have bookmarked.
After you tap on "Bookmarks", an overview (one box per question) comes up:
It lists the question text (here, the question was about four songs containing the word "white" in the title), the queston type (here, MatchTwo), a waste bin to delete it, and if the bookmark is locked (as in the example above), a blue button with a lock icon displays the remaining time until it is unlocked. A red badge indicates how much it would cost to unlock the URL immediately (the price starts at 3 coins and decreases with time).
The reason why Quizcover locks bookmarks for 30 minutes is that its developers don't want gameplay to be interrupted all the time. Very few users will actually pay for access to websites they could easily find with Google. In case you do hit the button, a popup asks you whether you really wish to spend coins on an immediate unlock:
After a bookmark has been unlocked (be it by the passage of time or a user spending coins), the blue button is removed from the related box of the bookmarks overview:
In that state (no more blue button), the bookmark can be opened by just tapping on it. Then a list of all post-solution items related to that question is shown, and you can tap on the links. When you do, a browser popup comes up, and when you're done reading, you automatically return to Quizcover.
This is what the bookmark details look like for the "white song" question (one would have to scroll to access additional items):