A:
The gerunds are usually used when the verb is currently being executed although for "understanding" it can either be a verb or an adjective
Wanting
"What's wrong with wanting to be part of the team?"
"Not wanting to see it means you're a coward"
For understanding
verb:
"Thank you for understanding me"
"Understanding the lesson gives you a higher chance to pass the test"
Understanding as an adjective
"You are very understanding"
"Your understanding attitude gives me hope that not everyone are judgmental"
Hope this helps