Let's simplify the expression:

$3a^3 b^2 - 5a^3 b^2$

Both terms have the same powers of $a$ and $b$, so we can factor them out:

$(3 - 5) a^3 b^2$

Simplifying inside the parentheses:

$-2 a^3 b^2$

So, the simplified expression is:

$-2a^3 b^2$

Let me know if you'd like more details or have any questions!

Here are some related questions you might find helpful:

1. How do you simplify expressions with like terms in algebra?
2. What is the distributive property, and how does it apply to simplifying expressions?
3. What is the difference between like and unlike terms?
4. How would the simplification change if there was a different exponent on $a$ or $b$?
5. How do you factor out common terms in an expression?

Tip: When simplifying expressions, always look for common factors in the terms. This will help you reduce the expression step by step!