The Guru

The Guru is the one who guides us along the path which connects us to the Divine,a path we all seem to have forgotten.He makes us realise that God lies within and and helps us to to realise Him.He is the one who brings about the union of the Atma with the Paratma.The Atma is the spirit,essentially a part of the Supreme Being.The Guru incarnates just to help those who are "ready'to journey on this path and it is only those who are 'ready" are fortunate enough to come in contact with him for his blessings,based on their Karmas.
The journey is simply beautiful and breathtaking and makes one realise the difference between "happiness" and "bliss".Happiness is a result of fulfillment of material desires while bliss is due to one's close proximity with Him.All this happens when the Guru "iniates'us by bestowing on us "Naam Daan",and teaching us to connect with Him by the Anhad Shabd(similar to The Word mentioned in the Bible,as this is supposed to be the origin of the world).This has been practised by Muslim sufis as well.

The Soul

The soul is the essence of our being,and continues from one incarnation to another and akin to our genetic make up.It is something like a very vibrant energy which is actually very powerful and,therefore,so close to the Divine!Blessed are those who can get a peek into their souls as then they are then in very close proximity to the Almighty.The soul is the "spirit'of God.