what is physics?

Definition of physics is subjective in nature...

But, as a physicist we can view physics as a subject which can be seen as subject of basic laws of nature and their manifestations in other phenomenones .

As per Dr Rp feyman, suppose you are watching chess game you don't know the rules but you can frame some rules by talking some observations by looking into the game .

Physics goes the same way. By observing the nature you can frame out some laws which govern this universe...and can use these laws to build some tools to interact with nature or for our personal uses...