Very general and broad information.
Banner management - this is a system where you feature a rotating selection of banners from advertisers who want to advertise on your site.
Income can be generated by monitoring 'click through' statistics where you get a fraction of a penny for every visitor your site refers, or in rare cases a tiny percentage of any orders placed from a visitor of your site going on to the site a banner on your page leads to.
It is easier if you keep a small database of banner images and use it to store all of the statistics as well.
You can get lots of free PHP and ASP banner management scripts for free and some you pay for.
Turnkey has been defined many times online click here
Basically it normaly refers to email campain, e-commerce systems, more rarely it can also feature in online Document Storage programs and so on that have been developed by a company or ISP and are sold to you on the basis that for a given cost you may use said system for your own business purposes.
This is a very, very brief description and the actual availability and implementation of Turnkey and Banner Management solutions varies wildly. The terms, loike possible explanations of them, can vary to a huge degree, but the above is a general overview and covers the very basics.