A binding is an association between a name and that which the name denotes. Bindings are established in a lexical environment or a dynamic environment by particular special operators.
An environment is a set of bindings and other information used during evaluation (e.g., to associate meanings with names).
Bindings in an environment are partitioned into namespaces. A single name can simultaneously have more than one associated binding per environment, but can have only one associated binding per namespace.
3.1.1.1 The Global Environment