The release comes a couple of weeks short of two years since the last release, Wheezy.
The biggest change in Jessie is the change in the default init system, which is now systemd. However, the old Sysvinit system is still supported for this release.
A media release from the project said this would result in faster boot times, cgroups for services and the possibility of isolating services.
Ten architectures are supported in this release: 32-bit PC / Intel IA-32 (i386), 64-bit PC / Intel EM64T / x86-64 (amd64), Motorola/IBM PowerPC (powerpc for older hardware and ppc64el for the new 64-bit (little-endian)), MIPS (mips (big-endian) and mipsel (little-endian)), IBM S/390 (64-bit s390x) and for ARM, armel and armhf for old and new 32-bit hardware, plus arm64 for the new 64-bit "AArch64" architecture.
Upgrading from Wheezy to Jessie is painless, but the project has urged those who plan to do so to first read the release notes for possible issues that may arise.