Quick answer
The fool finds evil fun; it is his recreation. The man of understanding finds the same delight in wisdom. What a person does for pleasure is one of the most honest windows into who they are.
Read both lines
The first line uses the word for laughter and play: doing evil is the fool's sport, and this is darker than it first appears; he does not sin reluctantly, dragged by circumstance, mischief is where he goes for fun. The second line answers: wisdom is the understanding man's delight, his version of the fool's sport. The surest diagnostic of a heart is not what it does under obligation but what it does for joy. Tell me what feels like play to you, and I will tell you who you are becoming.
Related: Proverbs 2:14 · Proverbs 15:21
New King James Version®, Copyright © 1982, Thomas Nelson. All rights reserved. Full copyright information. Scripture provided by API.Bible.
Go Deeper
If this verse has been used to put weight on you that it was never carrying, ask about it directly.