Changes

'''Variables''' are used to '''store information''' to be referenced and manipulated in a computer program.<br>They also provide a way of labeling data with a descriptive name, so our programs can be understood<br>more clearly by the reader and ourselves.<br>'''Reference: ''' https://launchschool.com/books/ruby/read/variables

'''User-defined variables''' are variables which can be '''created by the user''' and exist in the session.<br>This means that no one can access user-defined variables that have been set by another user,<br>and when the session is closed these variables expire.<br>'''Reference: ''' https://mariadb.com/kb/en/user-defined-variables/