How to make such a dialogue?

Question

css

Hello,
please tell me how can I make such a block, in this style:

Only there will be text inside it and it is desirable that it can be stretched in height.
I look on the Internet, but nothing fits, I don’t know what it’s called.
Thank you very much in advance!

Answer 1

cssdeck.com/labs/full/rchqydmj

Answer 2

Through a pseudo-element. This is the most practical way.