A Listing Plan is a time limited subscription assigned to a category(s) and available to a particular account type(s) (buyers, Dealers, Shps etc). Plans provide a wide selection of capabilities to you in terms of prices, duration of plans and ads, featuring ads and multimedia uploads.
Depending on type of a plan it allows you to add either a listing (single listing) or a few listings (listing package) within a set period. The plans also offer an upgrade-to-featured option for free and paid ads of all active ads. A package plan can offer both featured and standard listings.
So, you should decide if you want to add a single listing or a few ones and have an opportunity to feature some of your ads later.