A hydroponics system consists of a few key components. Because growing plants hydroponically means that they are grown in water rather than soil, a hydroponics system will need some type of reservoir to hold the water for the plants. The crowns of the plants will need to be suspended over the water and thus some mechanism for this will be needed in a hydroponics system. This varies depending on the hydroponics system that you choose, but might be some type of netting, or a plastic tray with one or more holes cut out of it, either of which allows the plants' roots to dangle below and into the water and the crowns of the plants to remain safely above water. Some type of a pump is needed to raise the water level up to the plant roots.
In addition, you will need some additional hydroponic gardening supplies such as plant nutrient, which is a water-soluble plant food needed for hydroponically grown plants, as well as lights for the plants. Plants also need light for photosynthesis and growth, and thus indoor gardeners will use a grow light for this purpose. A grow light may be an LED, HID or other type of strong light. The important aspect of the lights for your hydroponics system is that it needs to produce light in the spectrum that plants need for optimal growth: red/orange spectrum light for when they are mature and you want them to fruit or flower, or blue spectrum light for when they are small and growing vegetation, and to mimic as closely as possible natural sunlight. Certain lights that work well in a hydroponics system are available that offer a full color spectrum, so if you get those you will be covered no matter in which stage of growth your plants are. If you choose a HID light, the light will also need a digital ballast, which controls the electrical current that flows to the light bulb. You will also need additional hydroponic gardening supplies such as a reflector, which helps to increase the area of light. Air cooling systems are also needed because many types of light systems also create heat.
More information is available about hydroponic systems and hydroponic gardening supplies online from hydroponic discount suppliers.