Sometimes I'm very confused about what is life and death. Why are we living and why will we face death?
In Vedic shastras, there is detail explanation on what happens after death, what we have to do in our life, etc. But I didn't find about the true meanings of life and death.
Is it only "take birth", "live on earth" and finally "face death"?
It is commonly known that God is the eternal everlasting entity that is one without a second. Just like fire, although a single entity, has these two energies of light and heat, God also has these two special energies known as Jiva and Prakruti. Of these two we are the sentient jiva and everything else is insentient matter. So these three entities God, jiva and prakruti or maya are unborn and eternal:
jñājñau dvāvajāvīśanīśāvajā hyekā bhoktṛbhogyārthayuktā [Sve. Up. - 1.9]
Meaning
The knower (God) and the ignorant (jiva), are both unborn. She (i.e. prakruti) too is unborn who is connected with the enjoyer and the objects of enjoyment.
For a certain reason, the whole of the existence operates in a cyclic manner. So in course of time the existence appears, stays and then disappears. This has been going on continually and will continue to go on forever. So, utpati, sthiti, pralaya are the three aspects of the existence. Because part exhibits the nature of the whole, whatever exists in the existence also follows a similar pattern. So jivas take birth here, live for some while and then eventually die. After their detah they go on to other realms as per their actions and then again take birth here. So this is also going on cyclically. This cycle of repeated existence is known as samsara.
Just like from a campfire arise thousands of sparks, infinite number of jivas come from God and return to it (Mund. Up. - 2.1.1). But due to the existence of the other energy known as maya, the jiva once entering into samsara gets entangled in it and can not get out and return to its source. Until and unless a jiva returns back to God it will keep revolving in this material mode of existence taking birth again and death again infinite times:
punarapi jananaṃ punarapi maraṇaṃ punarapi jananī jaṭhare śayanam
iha saṃsāre bahudustāre kṛpayā apāre pāhi murāre [from Bhaja Govindam, by Adi Shankara]Meaning
Birth again and death again, into the mother's womb again,
Hard it is to cross this samsara Oh Murari, redeem me through your infinite grace.
So sages and saints suggest various ways so that we can obtain the liberation from this repeated cycle of death and birth. So yes, for an average person life is simply "take birth", "live on earth" and finally "face death", but for the wise, taking birth was inevitable, so also death, but whether to take birth again or not is dependent upon how he lives on earth. If he will not work to get out of the clutches of samsara, then obviously he will work to get more entangled in it.
Note: This is actually an existential question. So the answer can be varying and lengthy to explain. So I answered it briefly without including much scriptural references.
