The ego is that little voice inside your head that chatters a lot. It congratulates you on your accomplishments, it tells you you look sexy today, or like a loser, it keeps you up at night, it prevents potentially embarrassing situations. It makes you look stupid, it makes you look smart. It is neither inherently good nor bad.
Realizing the difference between YOU and your mental chatter(ego) changes your life. Before coming upon this revelation(which you could acquire many different ways and with different terminology), you wonder a lot if you're crazy! I still wonder that sometimes, but knowing that the voice that runs rampant in my head is just a small function of my self, rather than my actual self, makes me feel a lot more at peace. I now know that I don't have to believe every little thing that crosses my mind, judge myself for "stupid" thoughts, or take my thoughts to be reality, or let an anxious thought start a whirlwind of nervous tension that starts at my head and spreads throughout my entire body, and day, infecting those around me.
When is the last time you had a song stuck in your head that you don't even like? When is the last time you had a thought that you didn't actually believe or even want in your head?(such as a self deprecating notion, or an unfair snap judgment about someone based on their appearance). And how many times has that led to you judging yourself or getting depressed or worried?
Exposure to a myriad of different things like the average person has day to day is going to affect your mind. You may think you're immune to pop culture, or gossip, or social conditioning, or the people around you rubbing off on you, and if you think you are, I have some disappointing news for you... You're not.
You are going to think about things you don't want to think about (latest example for me would be Miley Cyrus twerking at the VMAs). Simply seeing something somewhere online or the television(I try my best to avoid those but they're everywhere!) is enough to make it pop up again later when you're trying to study for a test or fall asleep. Not mistaking these random, often nonsensical and certainly non-beneficial mental phantoms for YOU, means being more grounded in reality. Calmer, more in control of yourself. You are no longer tossed about by every little ride your brain tries to take you on. You can now let your thoughts pass you by and maybe even laugh a little at the ridiculous ones. You can pick and choose which ones you want to explore more, and which ones can be discarded or forgotten.
I've recently decided to beware of any of my own attempts to "live beyond ego". That is the biggest ego trap I have yet to encounter. Thinking that you have risen above the ego and are immune to its tricky tactics is the most sure fire way to find yourself trapped again, this time without an escape because you think you've already escaped! This mind stuff gets tricky.
It's an invaluable skill to be able to separate yourself from your inner narrator, or as I've heard it quite accurately described, your raving lunatic. But it is a useful tool we can utilize, so don't go getting an ego about having no ego! ;)