There is a Level Order for each Membership Level and this can be used to change the order in with the Membership Levels are ranked.
The higher the number is set, the higher the Membership Level will rank.
This will affect which After Login/After Registration page will appear to Members who are part of multiple Membership Levels. If a Member is a part of multiple Membership Levels, they will see the After Login/After Registration page that is tied to the Membership Level they are a part of with the highest Level Order.
Note that the Level Order can also be used to re-order the Membership Levels for the site admin. Changing the Order Levels will result in the Membership Levels being re-ordered based on the highest on top in the Membership Levels tab.