Hi, I can understand it may be difficult to define what is a relationship. As am mom, I would tell my son that he is in a “relationship” with a girl if they have met in person for a “date” several times, have both expressed an attraction towards each other, agreed to continue to see each other, and agreed to see each other EXCLUSIVELY. That is, they both agree they will only go out one dates with each other.
A date could be described as going out together to get to know each other better. It could be going out to a movie, dinner, a coffee shop, bowling, or some other activity you believe you both would enjoy...
Hope this is helpful, although I know it may be old-fashioned.