These are setting which deal specifically with using the site for eCommerce.
The Activate e-Commerce setting is a simple setting to force e-Commerce to become active. Normally it is activated whenever one of the eCommerce modules is activated.
The Use Simple Permissions setting completely changes the way Exponent permissions work, but can greatly speed up a web site with a huge amount of users or customers. When turned on, user and group permission no longer apply, the system simply sees each user as either an administrator or a basic user.
The Allow Large e-Commerce Tables setting changes the display of the Manage Customers, Products, and Orders pages to use ajax loading. This may slow down the display of those screens since each page must be loaded from the server, HOWEVER on larger databases the pages will crash or not be displayed due to the amount of data.
The Disable Unsecure Checkout Warning setting turns off the warning message if you are using a non-SSL (https://) site and still using eCommerce (NOT recommended)
The Default Currency setting selects the type of currency (symbol) used on the site.
This tab also contains a checklist with links for getting e-Commerce up and running on the site. e-Commerce also becomes active whenever any of the e-Commerce modules are activated.