, announcements are posts that are seen on the top of every page in a thread...if a thread has 12 pages, you'll see the annoucements on the top of each of those pages. Sticky posts, which also stay at the top of the page, are only on the top of the FIRST page. So, announcements, I feel , are generally things you want members to see on any page you go (like the announcement I made in 'Book 5 Characters' about people making sure to check the threads before possibly creating a redundant thread), whereas sticky threads are just threads that are getting a lot of hits (or that people would find more convenient if they were at the top of the list, so they don't have to search for them), such as my thread in 'The Great Hall' that Han Lin made sticky (my 'hugs' thread). It didn't need to be at the top of every page, as it wasn't telling the members something they needed to read, but as a sticky thread, it is on the top of the first page meaning posters don't have to search for it, which is all it needed. Hope that wasn't too confusing and hope that helped! 
That's my slant on it all anyway! 
~ Lizzy
