Control flow is the order in which code is executed. Code is executed from the first line to the last line, unless something in the code tells the interpreter to do something else. This occurs frequently when using conditionals, loops, and functions.
A JavaScript function is a piece of code that represents instructions that are saved in memory in order to be reused later.
To invoke (or call or execute) a function is to run the code that is inside the curly braces. This is done by listing the function name followed by parenthesis. If there are any parameters (see Q4) they will be placed inside of the parenthesis.
When defining a function, the parenthesis () are used to hold your parameters. A parameter is the information that is the input of a function. Not all funtions have parameters.