First question which strikes that how BIG is Big Data .
There is no place where big data does not exist, it is every where . Lets take one minute of data report across the world and see how many users order food delivery from Zomato or Swiggy , posting pictures on Instagram, watching videos on YouTube and many other .
From the above content we can imagine that such huge chunk of data is generating every minute. This is nothing but constant production of data from various medium like social media and different application.
Right now the amount of data is generating is around of 20-30 Zettabytes, so with this information we can imagine that how large , complex and difficult it will be to store and process.
So its not about what the amount and volume of data , but its actually how large number of data or dataset is being collected from different source and of different format.
I hope it will be help you.