We will be bringing down the shard for a restart on Wednesday, January 18th from 7:00AM to 8:00AM PDT (1500 to 1600 UTC)

What precisely is meant by a "restart"? Does this mean rebooting the involved hardware and re-loading the shard from the hard drives, or what?

I to would also like to know what this means.

Most likely this means like it sounds.

They shut down everything, and restart. Like you would a computer :p Cleans out any lingering memory issues.

I see your UTC is right this time, that's good. You used to be an hour out. Just got the half hour warning ingame.

It means they are purging the Cache of the cpu and Temporary files of the storage units
wich means you get a more responsive system out of your servers wich in term speeds up the game (in terms of logging in/out and instance swapping)

WOW !
Sounds great !

Now one wonders why in nearly two years, no one recalls this being done before.

Awww I was going to come in here and yell - YOU LOSE EVERYTHING! BWAHAHAHAHAHA!

Sorry - I'm on a post Launch Party hangover.... who's got the Aleve?

Who's got the what? That some kind of hangover cure?

Because a restart is done during updates and such. As this is not that there for its just a restart.