Cách sử dụng
"Opt in" means choosing to participate or join something voluntarily. It's usually used when there is a choice to join a program or service that you must agree to in order to be included. For example, when you sign up for a newsletter or subscription service, you may see a box to "opt in" by checking it. This means you choose to receive the newsletter or service. "Opt in" is the opposite of "opt out," which means you choose to not participate or be included.