ConfirmDependencies is the program that installs packages that are required for LMCE. For instance, when you add a new device, any packages that devices needs will be installed by ConfirmDependencies.
ConfirmDependencies will call the ConfirmDependencies_Debian.sh script with parameters for each package to install. These parameters include the repository the package can be found in, and this repo is added to the apt sources.list if it does not exist already.
ConfirmDependencies will also install development packages(packages checked as "Build from source" in the dependencies section of the package screen) if the device we are installing on is checked in the Development device data.