You leave them everywhere you walk, but recently the term “footprint” has being used to describe your impact upon the planet in broader terms than the impression of your feet. The most common one tossed around these days is our Carbon Footprint (see global climate change). A more recently developed spin on the footprint term is the Water Footprint: how much water you consume through your actions (directly and indirectly).
Of course you use water in your day-to-day life: you take a shower, drink water, water your lawn, et cetera. There is another way we use water: through the consumption of goods. The food we eat takes water to grow (a lot more than you might think). The clothes we wear come from crops that require water. Even the cars we drive require water-intensive processes to create them. Everything we do creates a ripple through the world and we can often take massive amounts of the most basic resource needed for survival on Earth: fresh water.