From the perspective of reincarnation, soul mates are people (souls) with whom we have had loving relationships in past lifetime experiences, whose paths we cross again now. There is a heart resonance, which is not limited by time or space and carries across lifetimes. Therefore, when you come across their energy now, there is immediate ease and an uncanny familiarity. You might even find yourself saying, "I just met so and so, and I feel like I've known them forever."
Keep in mind that loving past-life connections include souls who at other times may have been your friends, mothers, fathers, children, brothers, sisters, other relatives, partners, teachers, teammates or work colleagues. Considering we have loved many people in many roles over the course of many incarnations, there is the potential for numerous soul mate encounters in every lifetime. The idea that there is only one soul mate is a myth.
Meeting someone now whom you knew and loved in a prior lifetime comes with a special kind of comfort and connection. If the person you meet now was a past-life lover, it is even more compelling. Have fun figuring out how and when you might have known each other before! You will likely have some intuition about this if you don't overthink it.
However, it does not necessarily mean drop your life and run off with this person. What happens next has a lot of variables. It will be up to the two of you to get to know each other now, and to determine what kind of relationship, if any, best suits who you each are now. Not only do people change over the course of one lifetime, they also change lifetime to lifetime.
The bottom line of a soul-connected relationship, romantic or not, is mutual unconditional love. This is so special because you feel seen, understood, met, safe and supported. You won't agree with everything the other person says or does, but it's not about fixing them or vice versa. Loving and being loved for who you are sets the stage to fulfill your highest potential in this life, if you choose.
All unconditionally loving relationships are soulful. We all have the chance to develop new soulful love connections, which are special right now and may become soul mate "reunions" in future lives.