Potable water is water that is consumable for human intake. This kind of water is free of harmful bacteria, most contaminants, and soil. It is generally filtered by man-made systems that supply water to towns and cities, however some surface water including protected springs is potable right from the source.
Potable water has many uses including drinking water and as a core ingredient in all beverages, cooking, and bathing. Non-potable water has unlimited uses such as cleaning cars and watering plants however if the water is bacteria ridden it may be harmful if human contact occurs.
If you find yourself without potable water, such as the city water system has become contaminated or is not providing running water you should be able to collect surface water recently after a rain fall in pans. Boil this water either by stove or by small outdoor fire for about 15 minutes as this will remove most bacteria contaminants and make it relatively safe for drinking. If this water has sediment or debris in it filter it through some clothe or even small pebbles. If you are stranded and do not have access to fire sources to boil water in, seek sources of water that you see other animals drinking from. If the water is slightly brown it is merely dirt and soil build up, but if it is cloudy it has bacterial contamination. If animals are seen drinking from it and you have no other options you should be able to consume small amounts to remain hydrated. Also if a rainfall occurs you can collect rainfall in a container as it will contain minimal amounts of contamination.
Never drink water that is dark brown or cloudy and never drink water from a source that you know has been contaminated with human waste. Ocean water is not generally consumable due to the high salt content and can cause further dehydration. If you need to consume ocean water and there is no other source, attempt to find a way to filter some of the salt out first.
Writers Note: I offer this information as a way to explain potable water and its uses. Always use good judgment and only attempt to boil/filter unknown water in the event of access to no other water source. It is a good idea to fill sealed gallon jugs with filtered water for storage in your home so you are prepared in case of emergency. Consult expert sources in advance for more details on surviving without readily available potable water.