Question about self-hosted WordPress

I’m not new to WordPress.com but I am to wordpress.org. The theme I have is the normal one for wordpress.org and I do have some plugins.

I plan to have alot of media; slider gallery, feeds, feature galleries and the needed widgets.It is a musician, art, writing site.

What I’m confused on is

1)what is a menu?

2) What is a static page?

Here is the beginning of my site. I like the left column bar and the gallery pic (plus I added a video I made) http://payitforward2015.org/wordpress

3)but that white part that is blank between black top banner and gallery pic….what goes in there? I also have the shortcodes plugin.

4)can I use a background image for all pages?

That is a lot of questions, sorry about that. But, like I said, I’m a newbie to wordpress.org.
Thank you!!