A Linked Account is an ancount created in your Lamden Wallet by a website that you have approved to interact with your Lamden Wallet. This approval is done via a popup window when you visit the website.
Each website that you interact with will have it's own Linked Account. This lets you, as the user, control how much of your TAU that application has access to.
This is an example of what a linked account looks like in the Lamden Wallet.
This is an example of a customized linked account where the application has supplied a custom logo.
Decentrailized Applications (DAPPS)
DAPP are what applications that have a blockchain comnponent to them are commonly called. Any application that connects to your Lamden Wallet is referred to as a DAPP.