That's the equation that describes the splitting of water.
Reations that follow the general form
#color(blue)("AB" -> "A" + "B")#
In your case, you're dealing with the decomposition of water, which is usually referred to as the splitting of water.
Word equations simply decribe what's going on in a chemical reaction. In this case, you would say that
#"water is being separated into ogygen and hydrogen"#
You don't need to include stoichiometric coefficients in word equations, so you don't have something like two water molecules are being separated into two hydrogen molecules and one oxygen molecule.
Here's a video on how to go from word equations to balanced equations