This is Emily’s tattoo of the Ancient Greek aphorism “Know Thyself” (nosce te ipsum):
It means that to know and understand yourself if to be able to understand others. It also can be very literal in that it is just important to know who you are inside and out. I learned about this in my political philosophy class in college… I read Plato’s Republic and my professor gave a lecture on the quote “know thyself” and I loved it!