SEO Titles and Metas in SEO by Yoast

A couple of questions about SEO by Yoast: SEO Titles and Metas

1) In Post Types: meta robots: index, follow -- what does this mean?

2) In-Home: meta description -- am I supposed to write the site description here, or is it supposed to contain code? If it's supposed to contain code, what would that code be, because I wrote the description but I'm thinking I shouldn't have.

1 - Noindex means don't index that page. Follow means follow any links on the page. Maybe your Contact page would have these settings, but you don't want Noindex for posts.

2 - Yes, write a description to be used for your Home page. Not code, but real text describing your site and what it's about. This snippet of content is the 2 lines of text that show up under your site links in Google search results.