Each RUP iteration (cycle) consists of four phases: Inception, Elaboration, Construction, Transition.
Each phase has a goal to reach certain milestone in the project's development.
Inception: milestone is reached when we have project's goals researched and defined.
Elaboration: milestone is reached when we have project's Architecture (what is considered 'Architecture' depends on project, including project's size).
Construction: milestone is reached when we have first working version.
Transition: milestone is reached when we deliver the product to our customer.
As part of each phase there's one or more iterations within that phase as well.
See also: 'Talking Objects' Solutions' for initial Inception & Elaboration tools.