A note is an element of a Tinderbox file, it has a Title (Name), a Text body, and Attributes (the Name is itself an attribute). A note is best thought of as the 'atomic' entity of information within a Tinderbox file.
A note may also act as a prototype for other notes.
A note is edited via its Note window.
Many other aspects of Tinderbox such as agents, separators and adornments are effectively just specialised notes.
Notes are often also defined as Paths.
Any note containing other notes is a 'container'; put another way, a container is any note that has children/descendants. Agents are a special class of container, holding an alias to every note matching the query stored in their $AgentQuery attribute.