3-ring: Pages are easily removed and reinserted.
Strap: Good for theme albums. If you work on items out of order, you cannot easily rearrange the pages once you complete them.
Post: Bound by 2 or 3 steel post or screw pins. Complete pages in any order you want, and rearrange them later.
Spiral: Spiral metal ring holds pages together, similar to a notebook. Pages cannot be rearranged, and usually there aren’t any page protectors.
Tip: be sure the page protectors hold the true size of the paper. Some 12 x 12 albums have page protectors that are a bit smaller than 12 x 12, which can be very very frustrating to discover after you’ve already completed your page!