QEMU is the software that creates virtual hardware which guest operating systems run on top of. All (well, almost all — see note below[*]) the hardware that a guest OS has access to is actually written to some specifications in software — i.e. no physical hardware is involved. For the QEMU/KVM hypervisor, most of these devices are written in the QEMU source repository. A few devices are part of the KVM code in the Linux kernel. QEMU also handles a lot of host-specific stuff, like storage and networking for the virtual machines.
[* Exception: physical hardware devices assigned to guests.]
Many contributors to the QEMU and KVM projects meet at the annual KVM Forum conference to talk about new features, new developments, what changed since the last conference, etc.
The QEMU project released version 2.4 just a week before the 2015 edition of KVM Forum. I thought that was a good opportunity to gather a few developers and maintainers, and get them on video where we can see them speak about the improvements they made in the 2.4 release, and what we can expect in the 2.5 release.