Google's voice commands are impressively powerful but it doesn't always hear you right. While you can help it out a bit, it still gets wrong sometimes. When that happens, you can use the "No I said" command to fix a word.
The feature is actually pretty good at figuring out what word you're trying to correct. As you can see in the example above, when Google mishears the name "Whitson," I only need to say "No I said Whitson" to correct it. Google recognizes that "Gordon" is okay as is. It's not huge, but it's handy to correct a small error.