A boot environment is a bootable instance of the Oracle Solaris operating system image along with any other software packages installed in that image. You can maintain multiple boot environments on your systems, and each boot environment can have different software versions installed. You can backup the current boot environment, you can update software without any risk of loss of data or the system environment. You can also update a boot environment that is currently not active. Use the beadm(1M) utility to create and manage boot environments.
You can use zones which can help you to maintain multiple boot environments with different versions of software installed. Zones can be a huge advantage when you do not have to reboot the system to access another environment. You can also use kernel zones to maintain different versions of OS. Oracle Solaris allows you to have several non-global zones, several kernel zones, and non-global zones inside a kernel zone. You can easily ssh to one of the zones without rebooting the physical machine.
For more information about boot environments, see Creating and Administering Oracle Solaris 11.4 Boot Environments.