Any summery will be lacking.
Your choices are to read the patch notes, review the new wiki/Herald and review the VN boards or jump into the game and find out about the game by playing it a bit. That is how all noobs find out how things work and it is the best way for returning players to find out exactly how things work.
If you left before Ywain, to keep the server population up Mythic needed to continue to cluster but there was a huge problem. Each of the cluster character databases had grown so huge that Mythic could no longer combine databases, which meant that they could not continue to cluster.
The solution was to create a new server (Ywain) and have active players transfer all their characters to Ywain. This way the new server character database would only contain a relatively small number of characters and not characters from 8-year-old canceled accounts.
As some players had dozens of characters on the old clusters, Mythic needed to devise a plan for players to have more than just 10 characters on the new Ywain server. Mythic’s answer was to create 10 log in servers. This allows a player to transfer up to 100 toons per realm to the new Ywain (10 for each Ywain 1-10) and it also allowed for 10 housing areas per realm.
See the Herald transfer
info/FAQ page for info about transfers.
The following VN thread has some good/great info.
Subject: Very noobish questions
Google the following (cut and paste into google) to get more VN threads about 'returning' players.
returning site:http://vnboards.ign.com/daoc_general_board/b5176
gl
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The art of war is simple enough. Find out where your enemy is.
Get at him as soon as you can. Strike him as hard as you can,
and keep moving. - Ulysses S. Grant
Only the dead have seen the end of war - Plato