Catch vs Pick up
Is there any difference between these verbs when we are talking about something we didn't undertood?

Example:

Someone is doing a listening exercise and he couldn't understand some words. What does he say?

I didn't catch 2 words.
I didn't pick up 2 words.

I think this could work also in a phone call.

Example:

I didn't quite catch that.
I didn't quite pick up that.

Question

Catch vs Pick up
Is there any difference between these verbs when we are talking about something we didn't undertood?

Example:

Someone is doing a listening exercise and he couldn't understand some words. What does he say?

I didn't catch 2 words.
I didn't pick up 2 words.

I think this could work also in a phone call.

Example:

I didn't quite catch that.
I didn't quite pick up that.

Answer

We use 'catch' to mean understand or hear clearly.

'Pick up' means more to learn or to hear and maintain an interest.

So if you didn't understand what was being said, you would most often hear "I didn't quite catch those two words."

Answer

Catch : To capture or seize, especially after a chase , and of course you can find ano ther meaning of these word 
pick up : it is usually an action , to select or cull.