Here are main UFO concepts:
You define ECS Task Definition in
.ufo/resources/task_definitions/web.yml. You can use variables and ERB templating to build different definitions for dev and prod environments.
App, Role and Env
Most tools have the notion of an app and environment. UFO, like heroku, includes the role concept. Examples of roles are: web, worker, clock. The default role is web and will conventionally create an ELB. These are just examples, as you can name the roles other names also.
UFO supports a concept called layering so you can use the same code to build multiple environments like dev and prod. More details in the Layering Docs.