I can't say 100% how this works with Leappad 2 as we have the Leappad 1, however it is simple to use. Once you have the Leapfrog Connect software installed that comes with your leappad, you chose your device and go to the "App Center". Once there, it's just like shopping anywhere online - you add items to your cart. At checkout, enter the code that is on this card and the amount is applied to your order.
I haven't used it personally, but its for my 4 year old granddaughter, apparently she can go to the a web site from the leappad and pick her apps, and with mom's help can enter the card information and buy what they want. They are very happy with it, so it must be easy to use.
The app card is like a gift card- it comes with a code on the back. You enter the code onto Leapfrog's website, and then you have a $20 credit to download music, videos, games, or books. You can narrow your search based on product and search, for example, for only Leappad 2 apps. You must install the Leappad Connect software on you computer/Leappad before you can transfer the new apps to the Leappad. The Leappad Connect software is free with your Leappad.
The Leap Pad 2 is what I bought for our grandsons. My understanding is that the unit must be connected to the computer and the card allows download of apps online. At checkout you enter the code from the card and it is added to the order. A lot like shopping for anything online.
You buy the card and when it arrives open it and on it will be a code (similar to a credit card code). Go to leapfrog.com and you can buy a game, book, or video. Plug your Leappad 2 in and the item that you purchased will be downloaded into the device.
The App card is just a gift card. You can go onto Leapfrog and purchase games or "apps" with your credit card or this app card. It is worth 20.00. There were a few games below 10.00 but the most popular characters with games are 25.00. The app card will work with any of the LeapPad products. It is basically giving you a 20.00 credit on the Leapfrog site. It is super easy to download from the site. All you have to do is connect using the cable that comes with the product. The games are listed on the site as whether they are for LeapPad 1 or 2. I found the download process very simple. I ended up spending about 40.00 on the first download, so if you are buying for a grandchild, you might want to buy 2 app center cards. I think the games are expensive, but I must add onto my first review by saying that they are very good games and my 4 year old is able to sustain attention with the LeapPad for almost an hour and loves the games that I downloaded.
After you install the Leapfrog software you hook the pad up to the computer with the cable provided. Go on the LeapFrog web site and go to the APP CENTER. Use the code on the app card to purchase games. It's very similar to iTunes. As you buy apps your purchase will be deducted from your total and applied to the order.
Plug the leap pad into your computer. Make sure you set up account with Leap Frog. Go to the website that's on the card. You order the games through the website that's on the card. There's a code on the app card. Put that code in the promo code box when you're in your shopping cart. This is after you select the games/books you want. :) Games range in price from $5 to $25. Hope this helps!