If you're having trouble choosing between a Matted album and a Flush mount album for your wedding, it's very likely because it's confusing! (especially if you're not familiar with book-making) I'll share two examples below from my trusted album company, and I'll try to explain the difference between the two.
FLUSH - In a flush-mounted album, the print extends all the way to the edge of the page. The white that you see pictured above, is part of the print.
Flush-mounting allows for a slimmer volume, with slightly thinner pages. This style encourages a modern edge in the layout design because photographs can easily be placed anywhere on the page.
MATTED - A matted album tends to be a thicker, weightier book.
Smaller prints are mounted onto the page, and then a matte / liner is placed on top. The white that you see below is a separate layer surrounding the print. Simplicity is key with this style; you generally want to stick with one or two prints per page and a slow, measured pacing.
The matted layout is akin to museum presentation, giving each chosen photograph a certain weight and importance.
I am a big fan of both styles. If you are still having trouble choosing, consider this: (by no means a rule of thumb, but potentially helpful)... If you love design, tend to choose sleek modern decor, and if you like your photographs to be large, then a Flush album will likely be a good fit for you.
If you are a bit of a romantic, love old things, relish tradition, and hold a certain preciousness about photographs... then you will probably want a matted album.