my take on it

Soul Mates and Twin Flames are not the same thing. Soul Mates are other souls that have agreed to connect with you on this planet for a purpose. In some cases it is to clear up karma, in other cases it is to finish unfinished business, and for some it is to accomplish a particular goal together. These relationships may be a joy to be in or these relationships may be a pain in your life. Either way they are here for a reason.
When Soul Mates first meet they sometimes feel as if they already know each other. They may feel very familiar to each other. Soul Mates can have a beautiful relationship together, but it will take work. Soul Mate relationships may last a lifetime and others may only be for a particular purpose and be temporary. You can have more than one Soul Mate in a lifetime.
Twin Flames are very different and very rare. Twin Flames are two people in two separate bodies that share the same Soul. Twin Flames meet each other in their first incarnation so that they remember the soul frequency of the other being. They are then usually reunited on their last time to this planet. If Twin Flames meet before they are ready they can be the total opposite and not at all compatible. When Twin Flames meet and are ready for each other, it is the most enjoyable experience possible on Earth.
At this point, Twin Flames are almost identical. They truly compliment each other and it is a hardship for them to be apart. As an outside observer it is sometimes hard to distinguish the two people. They also have a very strong bond and often have telepathy with each other. Their lives even before meeting each other have many parallels. Again, meeting your Twin Flame is very rare on this planet.