This spread is one of the simplest to do because it requires only one card. You should do this using both the Major Arcana and Minor Arcana to give more information. When the Major Arcana is pulled in a love spread: this indicates engagements, breakups, betrayals. The Major Arcana makes up the big events in a relationship, including the beginning and end. The Minor Arcana refers more to simple day-to-day matters, small feelings that things may be off or small adjustments that need to be made to continue with the relationship. The suit of the Minor Arcana card you pull will also have an impact on the reading. Keep in mind, Cups refer mainly to emotions. Swords refer mainly to mental intuition. Wands refer mainly to spiritual matters. Pentacles refer mainly to issues of fiscal significance.
The single card is meant to show you the tone of your current relationship. You will have to have an understanding of the individual cards in a tarot deck to understand exactly what this reading means. For example, Three of Swords is never a good omen.