Vim: How to show the error message when there is a syntax error?

Question

I have a C file (or ruby file) and I have a syntax error. When I save there is a bar that appears on the left, and an arrow pointing to the line where the syntax error is. I have the syntastic vim plugin installed so I don't know if that is a native feature or if it comes from the plugin.

Now my question is: How can I see the error message from within vim?