Don't understand how to implement Ionic menus at all

I was going through the documentation for how to add a menu to your app and I got really confused. I did step 1, which was adding the menu to app.html :

 <ion-menu persistent="true"  id='menu' side="left" type='reveal' [content]="mycontent">
    some menu content
 </ion-menu> 
 <ion-nav #mycontent [root]="rootPage"></ion-nav>

But here are the things that really confused me :

1)Why does the menu content need to be attached to ion-nav ?
2)Why does the page that opens the menu need to be the root page ?
3)What does setting persistent to true do ?

Essentially, I want my application to have access to the menu by clicking a menu toggle button in the navbar of that page, and I want all my pages to be able to do this. Simple use case, just need help figuring it out. I just know for sure that I shouldn’t have to set up a button in every .html page and a corresponding openMenu() function in the .ts file to be able to use the menu

just generate an example with menu and see how it works:

ionic start myApp sidemenu

The problem with the side-menu template is that it’s a single page app and I’m working on a multiple page app. So now I’m trying to figure how to open the same menu in different pages

you have to add more pages in app.component.ts
then add those pages in app.html too
done

Okay here’s what I did :

I added this to every page which needs to access the menu -

<button ion-button menuToggle>
   <ion-icon name="menu"></ion-icon>
</button>

The problem is I can only see this menu toggle button in one page, and it disappears in the next. According to the docs, it’s only visible when that page is a root page. But doing

    this.navCtrl.setRoot(theOtherPage)

doesn’t allow you to leave the page, not to mention - I still can’t even see the menu toggle button