A wine that is grown, vinted and bottled on a single estate and usually bearing the name of the estate. A sign of quality. (A.k.a. Chateau bottled, Domaine bottled)
There is an incredibly broad range to wine quality, from mass-produced jug wines of unknown origin all the way to microclimate-based, small batch cult wines. When you look closely at what makes for a quality wine, the word terroir crops up quite a lot. Simply put, terroir means location, and where the wine was grown is one of the most important factors to consider. So knowing the origin of the wine -- of the grapes -- can tell you a lot about the wine. Another popular concept is "Wine is made in the vineyard". So a critical question would be: Whose vineyard?
The best wines are made by people who are intimately acquainted with the grapes and the vineyard. If you buy wine on the open market, you have no control and have to make the best of what's on offer. A better idea would be to contract with a grower with an assurance that the grapes would be cared for according to the winemaker's goals. Best of all is to own the vineyard (and have control of the vineyard manager's salary). Invariably, the best wines -- the coveted and raved about wines -- were raised from their infancy by the vineyard's parents, and yes, I know this analogy is a stretch. That way the winemaker and the vineyard manager form a team with a single-minded vision: to produce the best grapes possible that will beget the best wine possible.
When the chateau has total control over the vines and the winemaking, it makes sense to keep it all in-house. Age the wine, finish it, bottle it on the premises, and then give it any extra bottle ageing deemed appropriate. And if you're going to go to all that trouble, why not brag about it on the label?
One minor exception to this scenario is the very small winery that perhaps doesn't own the vineyard or a bottling line. It's not uncommon for a smaller winery to rent a vineyard over which they exert total control, and then hire a bottling rig when needed, often in the form of a truck-mounted unit. These wines, too, can be considered estate bottled, which puts them on the same plain as the better-funded wineries.
So if you see the words "Estate Bottled" on a label, remember that it's a mark of both authenticity and quality, and it's a difference that makes some wines special.