Seedlings and Meristems
In Orchid lingo, the word 'seedling' is often used to describe the size of the plant. A seedling size plant needs several years to attain blooming size. The correct use of the word 'seedling' refers to an orchid produced from seed crosses. A seed cross is made by placing pollen (male), on the stigmatic tissue (female) of an orchid flower. Seed produced Orchids usually have similar flowers (species), or very different flowers (particularly hybrids) depending on the genetics of their parents. As such, each seed cross plant will produce an unique flower for those who wish to have one of a kind plant, as each seedling is slightly genetically different from its siblings.
On the other hand, meristems or mericlones are tissue cultured to be exact replicas of the original plant. A piece of tissue from an individual plant is divided into many small pieces in the laboratory. This technique produces exact copies of awarded winning plants, so in actuality you possess the awarded plant, as your plant has grown from a piece of it. However, 'seedling' is still often used to describe the relative size of a meristem plant.
Seed crosses and meristems are in a sterile flask before they are "out on their own" in a pot. So two years from flask can be five years since pollination or tissue culturing.