A Strategy is a named set of roles — each one becoming its own Agent — that hand work off to each other by name. Once you've wired up a pattern like a Watcher handing off to a Builder, a Strategy lets you save it instead of rebuilding it from scratch next time.
Each role decides where it lives — see Root roles vs. their own workspace for that judgment call: attached directly to the project you're instantiating into, or given its own dedicated space when it needs its own history and its own checkout, separate from its siblings.
Instantiating a Strategy is a single step — give it a name, and every role's workspace, Agent, and hand-off is created and wired up for you, ready to run. A role's instructions can reference a sibling role by name — see Referencing sibling roles in a prompt.
Two strategies ship built in as a starting point — a Watcher/Addresser pair, and an Engineer/Reviewer pair — so you have something real to fork rather than a blank page. See Forking the built-in Watcher/Addresser and Engineer/Reviewer strategies.