The phrase "What do you understand by..." is used to ask someone for their interpretation or explanation of a concept, word, or idea. It is a way to inquire about someone's comprehension or meaning they assign to a particular subject. Essentially, it is asking, "What is your understanding or explanation of this?" This phrase invites the person to share their knowledge or perspective on the matter being discussed.

The term "meaning" itself refers to the thing one intends to convey, especially through language. It includes the significant quality or implication behind words, phrases, or communication that someone seeks to express.