You can use asterisks or underscores for emphasis.

Your mom is fat. Your mom is *fat*.

Your mom is really fat. Your mom is **really fat**.

And you can use the left-leaning single quote (that's the one on the ~ key on American keyboards) to denote areas of code that you don't want the Markdown parser to remove. That's how I show you what I write for my examples. Just put it at the beginning and the end of the section you don't want parsed, and it'll show up in a monospace font.