The Web Mall is where you purchase items, there are 6 seperate tabs along to top:
All Items | Development | Battle | Gems | Badge | Honor
Items in the Honor section require Honor points
Items in the Badge section require Badges
All the rest are purchased with Mall Points and some of those can also be purchased with Vouchers but not all.
More details about these types of curency and item types is available on the Currency page and the Items category pages respectively.
Items purchased at the Web Mall; unlike items won in a Treasure Box are initially unlocked and you can sell them in the Trading Center. However, gems as soon as you use them on a commander, will be locked to your account thereafter.
Web mall exclusive items
Web mall exclusive items, are items that can only be obtained by buying them in the web mall, and with no other way. These items are the following: