A workspace is at its most fundamental level simply a collection of one or more charts.
When you save a file in Sentient Trader you are saving a workspace, which includes all the charts that you have open at the time. And when you open a file you are opening a workspace, which is in turn a collection of charts.
The simplest workspace contains only one chart. All the sample workspaces (for the EOD trial version of Sentient Trader) contain a single chart, and so the terms workspace and chart are practically synonymous - one could say open a chart, or open a workspace, because of course the workspace is only a single chart, but it is better to think in terms of opening a workspace because when one starts working with more advanced workspaces the two terms are not synonymous at all.
Why would one have more than one chart in a workspace? There are various reasons:
Note that there is a maximum limit of six charts per workspace. The reason for this has to do with the way in which your computer's CPU is used to perform multi-threaded analysis tasks. More than six charts in a single workspace would require too much CPU time, and would make Sentient Trader a very anti-social application.
Analyses and trading decisions on all charts are updated when opening a workspace.
For more information on workspaces, take a look at this video: