At its most basic level, Flare is a 2D vector animation program. It allows you to place objects on the stage and animate their properties (e.g. position, scale, rotation).
All the objects that you place on the stage, or in an artboard, appear in the Hierarchy. The Hierarchy is a tree view, which shows the parent/child relationships between the items on the stage. These parent/child relationships are a core concept in Flare, which allow you to create complex layered animations with minimal effort. Nodes, Bones, and Solo objects can all have children in Flare.
Any type of object can be a parent or a child of another type of object. When an object is a child of another object, it inherits all the transformations of its parent.
The depth of these parent/child relationships is infinite, so you can keep stacking (or nesting) items to create grandchildren, great-grandchildren, and so on.
Read more on the Hierarchy page.
Bones offer an intuitive way to animate advanced characters with many connected parts. They follow the same hierarchical concepts discussed above, but they allow you to easily create a unique transform space (or pivot point) for your shapes while also keeping a consistent distance between parts (just like a real skeleton).
Read more on the Bones page.
There are two primary modes in Flare: Design and Animate. As the names imply, you want to design your graphics in Design mode and animate your character in Animate mode. Note that the interface changes to display the appropriate tools for each mode. For example, the Animations list appears in the Hierarchy Panel in Animate mode. Similarly, the Create Tools are only available in the Toolbar in Design mode.