A "pinky promise" or "pinky swear" is a cultural practice often used between friends or family members to signify that a promise has been made. It's typically performed by interlocking the pinky fingers of two people, each of whom has made a promise to the other.
In the context of a relationship or interaction with a guy, a pinky promise carries the same connotation—it represents a commitment to do something or keep a particular promise. It's an informal way of sealing a deal or promise, and it often symbolizes trust and respect between the two individuals involved.
The actual meaning, however, depends largely on the context and the specific promise that was made. For instance, you could pinky promise to keep a secret, to remain friends, to meet at a particular place and time, etc. The significance of the promise can range from casual to serious, depending on the situation.
Remember, even if the pinky promise seems cute or informal, it still represents a commitment, and it's important to respect that.