Think for a moment that every interaction that takes place online today is backed by a central authority that we trust.
It does not matter what you do since you are always trusting that someone is telling you the truth, be it the bank showing you the balance of your accounts, whatsapp telling you that your message has been sent or your antivirus saying that everything is fine in your computer.
In fact, there is always the risk that some information provider tends to make mistakes or wants to lie to you. That is why internet security today is a mess in which almost all services can be victims of hacking. Worst, we entrust them with more information over time.
Blockchain alleviates that. Thanks to this concept of distributed consensus, an incorruptible record of past and present events in the digital world can be created. All this without compromising your privacy.