Also known as the Teleological argument ( from greek telos which means purpose ).
This argument states that if we look around in the natural world we can’t help but noticing that everything or most things fit very well for the purpose/function they perform, like the sun for example, it has a mechanism to generate long lasting energy without requiring much interventions ( nuclear fusion ) , life wouldnt have thrived on earth without this energy. Another example is the eye or ear - how the eye interact with photons and transmit that information to the brain to build an image, all that so we as human can experience life in a specific and useful way.
All this bears evidence that there must be a creator or a designer to have put all the pieces perfectly together to have this complex, efficient, self-sustaining system.
Because looking elsewhere in the universe, things tend to be random and less-likely organized, of course i’m talking about entropy. In this chaotic universe we live in, to have such a beautiful system perfectly tuned to allow life and by consequence, consciousness to emerge from it would make most claim that it must have been designed by a divine architect - God.
This is an argument from an effect to its cause, causality as I like to call it.
Arguments against
Charles darwin (1809 - 82) theory of evolution in his book origin of species (1859) argues that the existence of a divine designer is not the only possible explanation of how animals and plants are so adapted and tuned to their functions. He showed how, by a process of survival of the fittest, animals and plants pass their characteristics to their offspring, meaning passing information to better equip the next generations. Later scientists were able to prove this mechanism of evolution in terms of inherited genes .
Of course this argument doesn’t account for non-sentient things, we have yet to find explanation for the world around us like planets, sun… so in no way this disproves God existence, it explains how but we still have to understand why that mechanism exists and where it might have come from.
Limitation
So far the argument tries to prove the existence of a divine designer but there is no reason to believe that one designer not a team of designers, designed it all. So the design argument alone cannot prove that the theist’s God rather than other God or gods exists.