Plants need water to survive, but not all plants absorb water as efficiently as others. Some can take it through their leaves and pass it along to the plant's root while others tend to take moisture directly through the soil. There are many ways to water a plant, each with their own benefits and drawbacks.
This method is the most simply and widely used. You just sprinkle water over the plant's leaves, allowing it to be absorbed as well as run off and saturate the soil around the plant. Plants living in temperate and moderate climates have leaves with fewer veins. These veins are the plant's vascular support system by which water is sent to the roots, so watering the leaves doesn't work quite as well with such plants. The benefit of this method is how easy it is. The detriment is that the vascular system will take in as much water as is provided regardless of whether or not it is needed. This can lead to over watering.
There are narrow gauge hoses that connect to a normal spigot or garden hose. These are called drip-irrigation tubes. They have tiny punctures across their lengths that slowly saturate their surroundings. It is not uncommon to have these tubes buried in the soil prior to planting a garden. By doing this, you can send water directly to a plant's root system rather than having to rely on the leaves' vascular action for transport. When taking water through the soil, the roots also absorb soil nutrients. The downside is that this method requires forethought and is not as effective with tropical and sub-tropical plants, which typically rely on obtaining moisture through their leaves.
Indirect saturation involves allowing water to slowly seep into the plant's surrounding soil so that it can take it in through the soil. This is different from root saturation in that this method does not involve watering the roots directly. An example of this method is placing a plant in an unglazed terracotta pot and then placing this pot in a pan or bowl of water. Terracotta is earthenware; it is highly porous and will slowly allow water to pass from the bowl to the soil as the slow dries, keeping the soil constantly moist. The benefit of this method is that the plant will stay saturated as long as the bowl contains water. The drawback is that it can only be used with potted plants.