Is past life talked about by various spiritual gurus true or it's a scam.. ? Do people who are alive now really lived some time back...and took birth again
Is past life real?
From the Bhagavad Gita:
TEXT 20: For the soul there is neither birth nor death at any time. He has not come into being, does not come into being, and will not come into being. He is unborn, eternal, ever-existing and primeval. He is not slain when the body is slain.
TEXT 22: As a person puts on new garments, giving up old ones, the soul similarly accepts new material bodies, giving up the old and useless ones.
Just to add to Ikshvaku's perfect answer:
Here there is mention that we have different births, although there is a distinction between us (living entities or in sanskrit atma) and the supreme being (the super soul or in sanskrit paramatma).
TEXT 4: Arjuna said: The sun-god Vivasvān is senior by birth to You. How am I to understand that in the beginning You instructed this science to him?
TEXT 5: The Personality of Godhead said: Many, many births both you and I have passed. I can remember all of them, but you cannot, O subduer of the enemy!
Here further to the origin and nature of the (living entitiy or in sanskrit atma) and how they get entangled in the (material energy or in sanskrit prakrit) basically while interacting with prakrit they (atma) create what we call their nature and later this very same nature pushes them to action (through desires, fears, conceptions etc)
more details here:
TEXT 8: The living entity in the material world carries his different conceptions of life from one body to another, as the air carries aromas. Thus he takes one kind of body and again quits it to take another.
TEXT 9: The living entity, thus taking another gross body, obtains a certain type of ear, eye, tongue, nose and sense of touch, which are grouped about the mind. He thus enjoys a particular set of sense objects.
TEXT 10: The foolish cannot understand how a living entity can quit his body, nor can they understand what sort of body he enjoys under the spell of the modes of nature. But one whose eyes are trained in knowledge can see all this.