The Difference Between “Both” and “Each.”

You need a context to be able to tell whether “each” refers to two things. For example, you could say that each hand has a glove on it, or each team member was in uniform.

Let’s assume the context implies two things. You still have an important difference between these two words:

“Both” refers to two things together.
“Each” refers to two things separately.

Here’s a good example of getting it wrong:

There is one [polar vortex] at both poles, and other planets have them too.

Sorry, each pole gets its own vortex.

Just for grins, here’s a Hubble photo of Saturn’s polar vortex.

Related image