Pump-action filters have an intake hose that draws the water from its source in a lake or stream, a filter housing, and an output tube that sends the clean water into your bottle. A manual arm allows you to quickly pump the water into your container.
A gravity filter has a bag you fill with water, then hang from a tree limb or other object. The water drips down through a filter into another container. This type of filter purifies a large quantity of water with little effort.
Plastic water bottles are light, durable, and inexpensive. Stainless-steel bottles are slightly heavier, more durable, and more expensive than plastic bottles.
Water reservoirs, or bladders, are flexible plastic bags that often have a tube you can clip to your backpack's shoulder strap, allowing you to drink easily and frequently while hiking. They come in large sizes that don't need filling as often as most bottles. Also, reservoirs are collapsible, freeing up room in your pack as they are emptied.
A water bottle/filter combo offers an easy, convenient way to stay hydrated. Simply fill the bottle with water, then drink. The filter is integrated into the straw. The disadvantage of this method is that you cannot filter a large quantity of water at one time.