Certain cards in the tarot naturally form into groups. These cards have unique meanings, but they also have a common identity with the other cards in their group. The two largest subgroups are the major arcanas and minor arcanas. The terms major and minor reflect the relative weights of these two groups.
A major arcana card represents an energy that is deep, strong, decisive or long-term. When a major arcana card appears in a reading, you have tapped into a powerful energy in some area of your life. The minor arcana cards do not carry the same weight, but they are still important.
One of the meanings of this card is attraction - being drawn toward a person, place or idea that is pleasing. As a minor arcana card, the Two of Cups tells you your attraction is probably based on surface elements such as common interests or sexual desire. The feelings are strong, but they're mainly coming from the give-and-take of everyday adventure - for now.
If you had drawn the Lovers instead, you would have to give this attraction greater weight. As a major arcana card, the Lovers implies this relationship is not simple. The attraction is coming from a deeper place. There are elements that go beyond the casual and require more understanding.
You could draw a minor arcana card in one reading and then draw a major arcana card about the same subject in a later reading. What started as minor has become more important over time. Similarly, a major matter can fade and lose its urgency as your life changes. You can assume that a major arcana card brings greater energy to whatever area it represents.