“The fact that we use water does not mean that we actually consume it.” What does this mean?

when we drink or bathe in water it is not "consumed" that is it still exists. it goes down the drain to be reprocessed or evaporated and returned to the earth as rain.

To consume the water as in this context means to drink it either directly or through our food. We can use water without drinking it or putting it in our food. We water our lawns, gardens, wash our cars, bodies, etc. Swim in it, etc.

We use water in lots of ways other than drinking it or eating it through food items.

One meaning of consume carries an idea of using so the thing no longer exists (use up or exhaust). we may employ water, but we do not remove it from existence. It is a misleading statement, because consume also means to eat or ingest. they have selected to employ the one meaning of "using up" rather than the expected meaning of ingesting, but they have done this on purpose to underline that our ingestion does not truly eliminate (use up).

different way of use

It means you didn't pay attention in class.