When we say this we mean at what eleveation or level on a tree. Many orchids do grow on trees, so the higher up in the trees a plant lives the more sun it gets and the less regular waterings it gets. The general surroundings are humid, breezy and warm and cool alternating at different times during the day. Circulating air is preferred by orchids because they're used to ventilation in nature. Orchids are used to going days and days without being watered of fussed over, and often endure incredible hardships and live through them.
Orchids are very hardy.
They get their nutrients from debris and nutrients that come to them either in the rain, on the surface of what they're growing on or by debris falling onto their roots. Many are designed so that they like to have frequent rains and dry periods. These have mechanisms to help them adapt to their environment. Orchids can live longer than we can. We've had orchids survive without being watered for weeks or even a month.