It contains a packaged version of your project. I found a blog entry mentioning it.
Before an Azure package can be deployed to the emulator it must first be packaged. Since v1.4 of the Windows Azure Tools, the
csx folder and its contents are no longer generated during compilation... So in order to force the generation of the
csx folder we need to specify that the package should be generated for the compute emulator within the Azure project file...
:: Deploying to the Azure Compute Emulator
Now that we have the
csx package folder generated after each compilation run we can use the CSRun command-line tool to deploy the folder to the emulator...