Question 558182
1.  Two Real-World Sets
Family-
kids and moms
The moms are a function of the kids because each kid has only one mom.  The mom is the function because she has more than one kid.
Football Team-
team and players
The team is a function of the players because each player is on only one team.  The team is the function because it has more than one player. 
2.  The difference between linear and nonlinear functions:
A linear function shows a constant rate of change between 2 variables:  Distance = rate * time is a linear function
A non-linear function does not have a constant rate of change between 2 variables:  area of a rectangle is non-linear function; height of a falling object is affected by the acceleration due to gravity.
Are linear/nonlinear equations the same as linear/nonlinear functions?  No
A function outputs a value for every input value while an equation sets two expressions equal and only specific values make the equation true.  An equation does not output a value.  
Real-life uses:
Function:  exponential growth and decay.  You input the time and rate of growth to calculate the result – the amount in the future
Equation:  using equation to calculate total cost of an item, if you know the cost and how much money you have, you can calculate the exact number of items you can buy.