Imagine a photo of a written poem:
An image-processing program can "understand" the digital image: It can read the jpg, change the picture completely (e.g.: change the colors slightly), without changing the meaning one level up. But it doesn't understand the characters or words.
An OCR program can read the image and "understand" the characters (or the textual representation. It can change the representation completely (save it as UTF-8 or whatever) without changing the meaning one level up. But it doesn't understand the language.
GPT-3.... well, let't go directly to humans
A human can read the text and understand the words and understand their meanings and what the sentences say. Another human really understands the poem and the subtext another level up.
I think understanding always works on different levels and is a part of communication.