Correct watering of plants is important for the general health; too much water and the roots can rot, too little water and the plant will be subjected to stress making it more prone to insect and other attack or even become desiccated and dry out leading to the plants death.
This moisture meter rapidly indicates the level of moisture in the soil and thus will guide the grower on watering schedules. This is particularly useful when:
you have purchased a new plant or orchid you are unfamiliar with
the growing medium was recently changed
water demand changes according to the season or action ie the plant has flowers, no leaves, you have just pruned it etc.
Basic instructions and chart are included with the meter.