An odd question, but also a very important one. Matter and energy are considered interchangeable entities. We try and understand our world by explaining things using comparisons, or sometimes just giving something a name makes us feel better. But stop and think... what is it that, no matter how advanced we become, or how technologically astute we are, we can never know? The answer my friend is matter. All else can be understood, but the substance which constitutes EVERYTHING will forever remain an enigma. Sure we can say that everything is made of atoms, and atoms are made of protons, neutrons, and electrons, and all that stuff is made up of smaller bits, and those are made of other smaller bits... but BITS of what?
So what, you say?
So, this is a big deal. This is the one major clue we have about ourselves and everything around us, including the universe. The fact that we cannot EVER understand what matter is, suggests that it's nature is a key...to explaining what and who we are, and what the universe really is...in short, what the hell is going on.