An entity is a named item with an associated name path, such as a function,
type, interface, or namespace. For example, in fn GetTime(), GetTime refers
to an entity which is a function.
An identifier is the token which names an entity, and is also used in code to
refer to the entity. For example, in fn GetTime(), GetTime is the identifier
for the function.
A library is a group of files that form an importable API and its
implementation. Carbon encourages small libraries, bundled into larger packages.
For example, given package Geometry library Shapes;, Shapes is a library in
the Geometry package.
A name path is the dot-separated identifier list that indicates a relative or
full path of a name. For example, given fn GetArea(var Geometry.Circle: x),
Geometry.Circle is a name path. GetArea is also a name path, albeit with
only one identifier needed.
A namespace is a entity that contains entities, and may be nested. For
example, given a name path of Geometry.Circle, Geometry is a namespace
containing Circle.
A package is a group of libraries in Carbon, and is the standard unit for
distribution. The package name also serves as the root namespace for all name
paths in its libraries. The package name should be a single, globally-unique
identifier. For example, given package Geometry; in a file, Geometry is the
package and root namespace.