There are many sources of information on this topic, and various ways to define the process, but it essentially comes down to a structured sequence of phases that are followed by an organization in their development of software workflow.Most sources settle on 6 or 7 distinct phases, currently, to the software development lifecycle.
And there are many more, with various approaches to the order that should be taken, and which functions should be defined within a phase.
Agile
Ultranauts encourages its projects to be run using the Agile SDLC methodology. While not all of our clients use it - or apply its advantages fully - several projects are set up to run full or modified Agile processes.