How would you describe being non-verbal

I (44 M) am autistic, but I am verbal. I started speaking with 3 years, and I don't remember how it was being non-verbal.

I have a friend with non-verbal child, and it got me curious about how is being non-verbal. I would love to read from this community how could you explain the feeling.

For example.. is it trouble finding the right words? Is it difficulty with the movement needed to pronounce? Is it about being overwhelmed and not being able to process anything?

I would love to hear your experiences and share it with my friend, so she can understand the struggles her son is going through.