Estate sales have their own section in the classifieds, and usually there are little signs posted on streetcorners in the area on sale days that are fancier and more professional than any garage sale notice.
While they can be sales of the belongings of someone who has passed, estate sales are also moving sales -- either way, there's a lot of personal property and household goods up for sale.
Sometimes it's an auction format; sometimes, it's not. Estate sales are run by professionals, and they're in the business to make a profit off the sale by taking a percentage of the proceeds.
You may think that means less of a bargain -- but these pros know how to mark the merchandise so it will move, and the last day or afternoon may see real markdowns on the pricing. Ask them when they'll be discounting the stuff - they'll tell you.
The best stuff will be gone quick - these estate sale pros will have notified their "regulars" (antique dealers, E-bay sellers, and the like) of their upcoming sale and those folk will be at the door right when it opens ... but you can find a lot of good things, cheap.
Is it better than a garage sale?
For someone who's moving, you betcha. If you're downsizing, let these pros handle your moving sale -- they'll do a much better job than you can on pricing and displaying the stuff, they'll find things you didn't know had such value because they know their markets, and they already have a solid customer base.
For someone who's buying, probably. You might find a rare first edition for two bits at a garage sale (the estate sales pro will know to check the books before they're offered) but prices aren't going to be that different at an estate sale, and you'll have lots more to choose from there.