The phrase "I couldn't care less" is an expression used to convey a lack of interest or concern about something. When someone says this, they are essentially stating that they have absolutely no interest, emotional investment, or regard for the subject or situation in question.
The phrase is often used in response to a statement or a question to emphasize the speaker's indifference or disinterest. For example, if someone is talking about a topic that doesn't matter to another person, they might respond with "I couldn't care less" to show that they have no desire to engage in the conversation or express any concern.
In some cases, people might say this phrase to assert their detachment from a situation or to make it clear that they don't want to be involved in the matter being discussed.
The phrase is often used colloquially and might be delivered with varying degrees of emphasis or tone, depending on the speaker's attitude and the context in which it is used.