Cattleya aurantiaca Bletia ensifolia Clowesia russelliana

What is an Orchid?

Here's the scientific definition: (see below for a less scientific answer)

Kingdom: Plantae - the taxonomic kingdom comprising all living or extinct plants
Plants are a major group of living things (about 300,000 species), including familiar organisms such as trees, flowers, herbs, and ferns. Aristotle divided all living things between plants, which generally do not move or have sensory organs, and animals.

Division: (formerly Phylum) Magnoliophyta

The flowering plants (also called angiosperms) are a major group of land plants. There are two groups in the seed plants.  The first: the flowering plants that cover their seeds by including them in a true fruit. Their reproductive organs are in a structure called a flower and the ovule is enclosed within a carpel, which will grow into a fruit.
The other major group of seed plants, called gymnosperms, the ovule is not enclosed at pollination and the seeds are not in a true fruit, although occasionally fleshy structures may cover the seed

Class: Liliopsida

The traditional scientific name for this group is Monocotyledones, although recently, it has been called Liliopsida. The traditional name Monocotyledones (or Monocotyledoneae) derives from the fact that most members of this group have one cotyledon, or embryonic leaf, in their seeds. This is opposed to the (traditional) Dicotyledones, which typically have two cotyledons. From a diagnostic point of view the number of cotyledons is neither a particularly handy nor reliable character.
Nevertheless, monocots are a distinctive group. One of the most noticeable traits is that a monocot's flower is trimerous, with the flower parts in threes or in multiples of three. For example, a monocot's flower could have three, six, or nine petals. Many monocots also have leaves with parallel veins.
The Monocotyledons or monocots are an extremely important group of flowering plants, dominating great parts of the earth and with many economically important plants.
The largest monocot family is the Orchidaceae (orchids), with very complex (and striking) flowers, for highly specific insect pollination.
The second largest and perhaps more notable family, the Poaceae or Gramineae (true grasses), have evolved in another direction, becoming highly specialized for wind pollination. Grasses produce small flowers, which may be gathered in highly visible plumes (inflorescences).

Order: Asparagales

The order of plants with irregular flowers having minute seeds. It includes the Families Orchidaceae and  Burmanniaceae. This order was formerly called Orchidales.

Family: Orchidaceae

An enormous cosmopolitan family of perennial terrestrial or epiphytic plants (occasionally lithophytic and saprophytic) with fleshy tubers or rootstocks and unusual flowers. They are characterized as having 3 sepals and 3 petals, one of which is shaped differently than the other two.

The orchid family (Orchidaceae) is subdivided in several subfamilies, and then into tribes, subtribes, alliances and then genera, (Genus) and Specie. The botanical name is the Genus and specie.

The Less Scientific Definition:

An orchid is the flower of a plant where the seeds are inside a "fruit" (we call it a seed pod). Orchids are pollinated mostly by insects. The seeds are very tiny, and when the seeds first sprout, they have only one embryo leaf. The flower has 3 sepals and 3 petals. The 3 sepals and two of the petals look alike. The third petal is shaped differently. Orchids can be very small or very large, and the colors of orchid blossoms can be any color or color combination imaginable.