The Global Stage Lifecycle (GSL) is the lifecycle that items follow that controls which versions are included in configurations and builds of the project. Item revisions are moved to the next stage in this lifecycle when they have reached the appropriate stage of approval (a process called deployment). This lifecycle is defined for the base database. Deployment areas for a project can be associated with these stages so that item files are copied to those areas when they are deployed to the corresponding stage.
If you are using Serena Deployment Automation (SDA) you can map GSL stages to SDA pipelines and environments. For information about using SDA see the Deployment Guide.