The difference between a software deployment being available and required in SCCM is simple. Available software appears in SCCM client (Software Centre) but doesn’t automatically install. The user may then choose to install it from the SCCM client. Required software gets automatically installed by the SCCM client whether the user wants it or not. Required software will be installed before the deadline.
… And that’s the difference between available and required software in SCCM 🙂