Now you know. The six characters in the tuning-name indicate the notes that each string should be tuned to, from low to high. This means that the lowest string should sound as an E , the next as an A etc. Any other indication for the tunings works the same way. To tune your guitar properly, you need a tuning fork or an electronic tuning apparatus.
Most people are only concerned with relative tuning.
I'll explain for standard tuning. It doesn't really matter how the lowest string is tuned. It just has to sound rather low, because otherwise the high strings could snap while tuning them later. We now act as if this lowest string sounds like an E , and tune the rest of the strings relative to this one. The lowest string is the sixth, so the fifth string should be an A .