I've been following the Rails 3 Getting Started guide and there was this note in the guide that I didn't understand:

In previous versions of Rails, you had to use <%=h post.name %> so that any HTML would be escaped before being inserted into the page. In Rails 3.0, this is now the default. To get unescaped HTML, you now use <%= raw post.name %>.

I don't really get what it means by escaped HTML vs unescaped HTML. Can someone explain this to me?

Thanks!