Hi! The Town Tune Eggs are collectibles, which are the little pictures on your sidebar (I see there is nothing there atm). They don't have any functionality beyond making your sidebar (to the left of your post on desktop and above on mobile) look cool.
TBT is the virtual currency of the forums and is officially called "bells", we just call them TBT to distinguish them from the bells in Animal Crossing. You can get TBT by making posts in eligible threads, or making threads in certain boards yourself! Other ways include selling collectibles, art, in-game items, etc.
Currently there is an Egg Hunt event going on, where you get egg currency (kind of like TBT) by searching the forums for them! It's real challenging, believe me. This egg currency can be used later for egg collectibles, like the Town Tune Eggs in my sidebar. But you can't spend the egg currency until you have picked a "basket", which gives you access to 6 of the 12 egg collectibles available. Check
here for clarifying information on the event.
I do hope all of this helps you! I'm genuinely curious about how/why you found my thread lol.
