Edge has its own blockchain, developed end-to-end by the core team. The chain is called the Edge Ledger, and it is this that $XE runs on.
Layer 2 is a collective term for solutions designed to help scale your application by handling transactions off of the main Ethereum chain (layer 1). Transaction speed suffers when the network is busy, which slows down processing and also increases the cost of transactions.
$XE currently runs as a layer 2 solution, which enables fast and free transactions wihtin the Edge Network, which are essentual to the running of the technology.
The Edge Network is a completely unique technology stack, originated by the core team and developed over many years. It is predominantly written in Golang.
Edge's source code is currently partially open source, with plans for going fully open source in motion. You can access projects code repository on Github at: github.com/edge