a sticky thread is one that the moderators have chosen to keep always at the top of that particular forum. as for the free apps, there are hundreds out there. Many of them are found in the aftermarket section of this very site.
I can assure you that your question is far from the dumbest ever (as there is no such thing here!) Sticky Threads are very useful frequent information listed at the top of each thread where they will not disappear. If you go the the 8100 Series forum the most frequently used information will be stickied at the top of the thread (they are a different color) that same for the 7100 series forum, media, etc.