In slang, "BET" is often used to mean "okay" or "agreed." It can also be used to express understanding or acknowledgment. For example, if someone says they'll meet you at 3 pm, you might respond with "BET" to indicate that you understand and agree to the plan.
In texting, "bet" is often used as slang for "sure" or "okay." It is a shortened version of the phrase "I bet," and it is used to indicate agreement or confirmation. This slang can also be used as a way to express agreement or to confirm something.