Let's break down the given expressions one by one:

1. Expression 1: $2 + ab$

   • This is simply the sum of 2 and the product of $a$ and $b$. The expression does not simplify further unless values for $a$ and $b$ are provided.

2. Expression 2: $a^2 - b^2$

   • This is a difference of squares, which can be factored as: $a^2 - b^2 = (a - b)(a + b)$
   • This is the factored form of the expression.

3. Expression 3: $(a + b)^2$

   • This is a perfect square trinomial, and it expands as: $(a + b)^2 = a^2 + 2ab + b^2$
   • This is the expanded form.

So, the expressions are:

1. $2 + ab$
2. $(a - b)(a + b)$ (factored form of $a^2 - b^2$)
3. $a^2 + 2ab + b^2$ (expanded form of $(a + b)^2$)

Do you need more details or explanations? Here are five related questions:

1. How do you factor other types of polynomials like $a^3 - b^3$?
2. Can you find the values of $a$ and $b$ for specific results of $2 + ab$?
3. What is the geometric interpretation of a difference of squares?
4. How do you solve quadratic equations derived from expressions like $(a + b)^2$?
5. How can the perfect square formula be applied to solve real-world problems?

Tip: Always check if you can factor or expand expressions to simplify or solve them!