What's the difference between aphasia and dysarthria?

Lack vs garbled: Aphasia is lack of ability to communicate. Dysarthria is garbled or unintelligible speech. Both are common complications of a stroke.

A lot: Aphasia is the loss of a previously intact ability to generate or understand language. Dysarthria is usually explained as "slurred speech" although that's an oversimplification; language is unimpaired. They can occur separately or together. Dysarthria is a motor deficit; aphasia is a disorder of cognition. You live down the road from the stanford stroke center. They are a good resource.