Karma is believed to be that phenomenon which means someone's deeds or speech is reflected in their very own spirit and then it builds the consequences for that person; also it decides the cycle of rebirth or total salvation to the soul. Many philosophers, thinkers and soteriologies believe that a person's future would depend on present day's actions & decisions.

Karma has two functions mainly: 

• it provides the motivation to live a moral life
• serves as the primary explanation of the existence of evil.

The 'reality' of this phenomenon doesn't depend on any religious theory, scriptures or Gurus. We may observe it in our day to day life. 

YES! Karma is real and very much exists. 

It could be witnessed as something when you do something you are motivated to carry it forward and do much better in other aspects of your life. But when you do something bad the mind gets regulated in a way to do more bad and don't improve from your current situation.

Thus, a good act encourages more goodness while a bad act encourages more immoral behaviour; and despite of knowing what is good you are tempted to choose what seems easy.

Hence, from here your actions/speech will bear the fruits of your future life. Those who continue to worsen their actions worsen the purity of their soul too. And those who make mistakes, learn from them and make an attempt to improve themselves create a glorious path for themselves in the future.