basically, yes. The extreme end of this is all grain brewing, where you don't use any extract.
There are a number of things that become more important as you begin to use more grain and less extract. For example:
- using the right amount of water for the amount of grain
- hitting and holding the temp of the grain/water mix (the mash)
- proper rinsing of the grain when done mashing to get the sugars into the kettle
Look up "partial mash". That's a half-way point between extract brewing and all grain brewing. You will conduct a small mash of grain to get some of the fermentables and then supplement the wort with extract to get the gravity you are after.