What is a JuMP VariableRef?

DRAFT: A JuMP variable is a reference to an index in a model. It's a thin wrapper around MOI.VariableIndex. Variables have (1) names, and (2) attributes. Describe the different scopes of a variable (e.g., as Julia variables, lookup by string name, and lookup by symbol).

The @variable macro

DRAFT: Describe the complete syntax of the @variable macro. Anonymous versus named variables. Describe the three possible container types returned and how to use them (Array, JuMPArray, and Dict).

How to delete variables.