Orchids have developed many resources to attract different pollinators. Nectar is one of the most prominent of those. Many floral parts have developed to great extent to contain the nectar and to attract pollinators with their own mechanisms.
A unique and not so common way to attract pollinators is by providing nectar in grooves or channels on the surface of the lip, the most exposed floral part. As the pollinators land on the lip, the shiny wet grooves or channels lead them to the pollinarium to help in pollination.
In orchid flowers, the basal part of the lip is often lobed, curved up to form a narrow structure with the column running along its open upper side. The apex part of the lip plays the role of a landing pad where the pollinator lands. The odour of the flower, the presence of pseudopollen, or the nectary glands make the pollinator crawl further inside. The anther cap is attached in such a way that it allows the pollinator to move forward without any obstruction. As the pollinator forces its way back, the pollinarium gets attached to the thorax of the pollinator and carried away.
(Note: Explained here is one of the several methods of the process of pollination in orchids.)