All Grain Brewing

As mentioned, all-grain brewing replaces the DME (and LME) used in the brew-day part of extract brewing. However, I thought it might be helpful to call out a some exceptions and related concepts that might be helpful as you're getting started.

Firstly, DME isn't necessarily 100% absent from all-grain brewing. DME is often used when making yeast starters and occasionally when bottling, even for all-grain beers. This can be avoided by collecting some of your wort to save for these purposes but my impression is that that's not super common.

Next, it's worth calling out partial mash brewing as a kind if hybrid process where you perform a (smaller) mash and then add extract to bump your gravity up the rest of the way. There are some nice advantages to this approach:

• If your mash efficiency comes out a little lower than you were expecting, it's not as bad if, say, 40% of your fermentables came from extract.
• If you have a small mash tun, this can help you produce a full batch of higher gravity beer without needing to upgrade your system. (Slightly unrelated, I have future plans to make a barleywine-adjacent braggot this way, using honey instead of extract.)

All of that is to say: all-grain means your "recipe" malt bill is all grains, but not necessarily that extract is not used at all. But partial mash can be a nice in-between option that mixes the benefits of all-grain and extract brewing.

Yes, your thinking is on the right track. Mashing with crushed grains at an appropriate temperature (about 150 F or 65 C) for at least 45-60 minutes then draining off basically creates your own "extract" so you don't need to add any DME or other sugars. From there you will continue to boil and add hops and brew in the normal way.

For a great introduction on how to brew, you might want to visit howtobrew.com(!). This is a good free website that should answer most of your questions about brewing including all-grain methods.