The Hindu trinity of Brahma, Vishnu and Shiva symbolize the forces of Creation, Sustenance and Destruction. We see these forces at play in our every day life. There is birth (Janam), life (Jivan) and death (Mrityu). This applies to all forms of life. This phenomenon is always in motion and forever changing.
For example, this ever-changing phenomenon is evinced in the cycle of water vapors originating from the oceans in becoming clouds and then rain. The raindrops again change form - from becoming a small brook forming into a stream, the droplets eventually merge with the rivers and flow back into the mighty Ocean from whose womb will ascend the vapors all over again.
The play of these forces is also evident in our thought process. In our society people are classified into various titles (Upadhies) depending upon their level of awareness and intellect. Without this classification communication and negotiation will become difficult.
However, viewed minutely, it will be noted that per se, we do not think. Our so-called thought process is the play of the three forces being discussed here. This can be tested by anyone. Try being silent and see what happens!
Brahma hurls! One after the other thoughts flow like an endless chain. The sequence may be random, erratic or a continuous pattern (for some time) but like a perennial river, the thought flow goes on. Brahma hurls.
Although this flow is continuous, seemingly it comes to a "Stop". The play of Vishnu begins here. This happens due to our beginning to entertain a particular or a segment of the chain of thoughts. Our dwelling on the thought is dependent upon our traits, character and upbringing, past experiences and also by the fact that Time, Space and Causation bind us. This is where the playful Vishnu, also culminates our dwelling or entertainment of thought into desires and passions that eventually lead to action. The birth of Karma takes place. Vishnu plays.
Try hard, as one may, we cannot keep on entertaining a thought or performing any action endlessly. The playful Vishnu must rest!
This apparent rest is due to the dissolution process of Shiva's force. Shiva terminates! Call it a simple end, a sleeping time or termination of the thought process, Shiva takes over.
But does it truly end? Awakening from the deep slumber, we find Brahma knocking at the door, hurling all over again for Vishnu to play and Shiva to terminate.
Verily, all this is Maya - an illusion.
Guru Nanak in his Japuji Sahib has appropriately explained this phenomenon:
Eka Mai Jugat Viyaee Tin Chele Parvan
Ik Sansari Ik Bhandari Ik Lavey Diban
Jiv Tis Bhave Tivey Chalavey Jiv Hove Phurman
Ohu Vekhe Ona Nadar Na Aavey Bahuta Ehu Vidan
The Supreme spirit manifested Maya
Who conceived and delivered the Holy Triad
The Creator, the Sustainer and the Destroyer
Yet He ordains as pleases Him for the Triad to act
Even they see Him not Who Sees All
This remains the greatest wonder of all