While I don't profess to understand fully Einstein's Theory of Relativity, I have my own take on the term. This is more philosophical than scientific (and I certainly don't claim to be a philosopher!).
As I age, I come to discover new observations in life, not only my own, but in general. For the past 20 years (and I can almost date it exactly), my motto has been to "simplify". Like the song says, "give me the simple life". I think I've been successful at attaining that philosophy.
Recently, I've added a new concept or belief: Everything is relative. I mean EVERYTHING is relative! Think about it.
How "rich" are you? Some people are richer, some poorer. How much do you weigh? If you're overweight, some people are more so than you. Where do you live? Some live in better places (both in terms of housing and geography/location), some worse.
I have rather suddenly realized (although I always knew it) that we live a life of comparisons. More or less. Better or worse. Bigger or smaller. Higher or lower. We frequently compare our lives and possessions to others. It's a chapter in "keeping up with the Joneses".
We're consequently good at rationalizing our positions or status in life. Yes, they have this, but I have that. We do it with occupations, religious beliefs, health, everything. If we can't change things, we give excuses or rationalize the situation.
We might be happy and satisfied with "where we're at". If things aren't "good", we often say "things could be worse". It's all relative. Right now, I'm thinking about gasoline prices. It cost me $60 yesterday to fill up. It used to be $30. It could (and might) be worse-$90.
I'm currently in a state of mind that compares almost everything to an alternative. That's not all bad, but it's driving me crazy--okay, crazier. See, that's relative!
I tend to gravitate to Nature and animals there is peace.