Before we’re born into this life, we make agreements – soul contracts – with other souls and agree to learn certain lessons from each other. We may establish a soul agreement with someone in order to awaken a particular facet of our soul that up to that point in time had laid dormant. We may be here in this lifetime to work through karmic issues we shared with this soul in another life (or several).
Most of us have many soul mates (they can be a friend, partner, sibling, co-worker). Not everyone we encounter has a soul contract with us, though.