Equations are ways of expressing the value of some concept relative to how one or more other variables change. For example, speed equals distance divided by time. The word "equals" makes it an equation. What's on the left is the same as what's on the right. If I am traveling at 60 kilometers per hour, it means that in one hour I will have traveled 60 kilometers (not necessarily in a straight line). 60km per hour equals 60 kilometers divided by 1 hour. You can see that this also means that if I travel a total of 240km in one driving session (not recommended), then I check and see that it took me 4 hours, the equation allows me to determing that I drove at 240km/4hrs, or 60 mph.
Math is the language of most sciences. Equations help us determine how changes in one thing lead to predictable changes in other things. From there, the sky is the limit.