Let’s take a quick dip into the nomenclature pool… It’s always good to know at least the basics, it actually makes it easier to know what you are looking at when you read about orchids. For example, if you see the name of an orchid where the species name is written in lowercase you know it is a pure species. Although, many people are pretty sloppy about this (even people who sell orchids), which makes it a bit harder. I am guilty of a level of sloppiness myself when I blog, but I do at least endeavor to capitalize correctly.

Family A taxonomic rank used for evolutionary, palaeontological and generic studies because they are more stable than lower taxonomic levels such as genera and species. Orchids belong to the Orchidaceae family.
Subfamily Families are further divided into sub families based on the ancestral relations between organisms. The five sub families under Orchidaceae are: Apostasioideae, Cypripedioideae, Epidendroideae, Orchidoideae and Vanilloideae.
Alliance A group of similar genera. For example the Cattleya Alliance, which include the following genera: Brassavola, ×Brassocattleya, Broughtonia, Cattleya, Encyclia, Guarianthe, Laelia, Myrmecophila, Sophronitis.
Genus A group of related species (genetically similar plants), both naturally occurring families and hybrids. Names are capitalized and written in italics or underscored (plural = genera). For example: Cattleya, or Ascocenda (where Ascocenda is a cross between Ascocentrum x Vanda).
Subgenus A taxonomic category ranking between a genus and a species. A subgeneric name can (but it is not customary) be used independently or included in a species name, in parentheses, placed between the generic and specific name. For example: Paphiopedilum (Parvisepalum) delenatii. Where Paphiopedilum delenatii belongs to the subgenus Parvisepalum.
Species The second term in a name of orchids that occur naturally in the wild. It is a genetically unique plant with a lineage that can be traced back to one common ancestor. The species name is written in lower case and in italics. For example: falcata in the name Neofinetia falcata.
Subspecies A subspecies has definable differences from the species and is more distinct than a variety but with enough genetic similarity that it will not be classed as a new species. It seems that subspecies is mainly used when variety and form do not provide enough distinction. Subspecies are limited to a distinct geographical area which is often reflected in the name. Abbreviated subsp. or ssp.
Variation A variation (var.) epithet distinguishes between the typical appearance of the species and a variation within the species. A variation have significant horticultural differences from the typical species, such as growth habitat or size for example, and is only found is a fraction of the general population. Variations are not limited to a distinct geographical area. Just as a species is a more distinct description than a genus, a variety is a more distinct description than a form. For example Cattleya walkeriana f. alba is a white (or white and green) version of the species. The epithet (alba) is italicized but “var.” of “f.” is not .
Form A form (f.) epithet distinguishes between the typical appearance of the species and sporadically occurring mutations that can sometimes be found within the broad population of the species. A form is often used to denote color variations (the alba form for example). For example Euanthe sanderiana f. alba is a white (or white and green) version of the species. The epithet (alba) is italicized but the abbreviation “f.”  for form is not. It is pronounced “the alba form of Euanthe sanderiana.” (For some reason Kew has decided not to recognize these var./form definitions as accepted names, but it is still widely used among growers as the attributes are definite selling points and as a buyer I would definitely like to know what form I am actually getting…)
Hybrid Man made crosses. Hybrid names are capitalized and not italicized. For example: Masdevallia Aquarius is a registered cross between Masdevallia urosalpinx x Masdevallia davisii. The creator can name the hybrid he creates when registering the cross. If the hybrid is unregistered, the parents are written in parentheses listing the seed parent first then the pollen parent separated with an x. For example: Paphiopedilum (haynaldianum x sanderianum). Different color forms are not spelled out when it comes to hybrids, but growers often put the color in parentheses behind the name to indicate what they are actually selling. For example: Ascocenda Princess Mikasa (blue).
Natural hybrid These crosses occur naturally in the wild. Indicated by an “x” before the species name and written in lower case and in italics. For example, Masdevallia × alvaroi – a natural hybrid between Masdevallia amanda and Masdevallia picturata.
Primary hybrid Crosses between two pure species. Hybrid names are capitalized and not italicized. For example: Paphiopedilum Dellaina is a registered primary hybrid between Paphiopedilum delenatii x Paphiopedilum chamberlainianum.
Intergeneric hybrid Hybrids between different genera. Names are capitalized and written in italics or underscored. Some have even been given new names, for example, Odontonia (Miltonia x Odontoglossum).
Grex From the Latin noun grex (= flock) is used to expand the Linnean binomial system to include horticultural hybrids. It is a registered hybrid’s identity. It is capitalized and not italicized. For example: Phalaenopsis Mini Mark, a cross between Phalaenopsis Micro Nova (P. maculata x P. parishii) and P. philippinense.
Cultivar ⁄ Clone Identifies a single unique plant and all of its divisions or propagations, including mericlones since a close is an exact remake of the genetic code of the source. The cultivar or clonal name is capitalized, not italicized and always found in single quotes. For example: Phalaenopsis Mini Mark ‘Holm’, or Ascocentrum miniatum ‘Kai-Gold’.