Let me clarify my answer since it is lower quality than people may like. To answer the question, my friend is a horticulist and has given a more detailed answer.
Subspecies is the most generic, taxonomically-defined term one rank order lower than species. The subspecies (either an individual subspecies, or collective group of subspecies) are defined to be genetically or morphologically distinct among other subspecies belonging to the same species, yet still produce viable offspring from interbreeding. For example, every type of dog is a sub-species of Canis familiaris, and all dogs are capable of breeding with each other. Subspecies, abbreviated Ssp, may refer to an individual subspecies type, or a collective group of related subspecies when a distinct subset is difficult to define or unknown.
There are a variety of terms that are analogous to subspecies, when the strict definition does not apply, or a different term has been used historically. For example, a varietal is the botanical term, and refers to a named subspecies. For example, grapes are a family of species, divided into the various subspecies, and a varietal is a specific subspecies that we refer to by a more common or familiar name, such as Riesling, Chardonnay, etc. (Grapes are a slightly different case in which most grapes are produced from hybrids or crosses for reasons of withstanding environmental conditions avoiding insect prey and fungal infections.) Microbiology has yet another distinction, called a strain. Strains are often genetically different, and yet all belong to a species. For example, several E. coli strains exist. In contrast, viruses are also given strain/subspecies names which don't technically fit the ICZN definition of interbreeding. Cultivar is a similar term, also from the field of botany. Cultivar is specifically applied to plants that are grown for some agricultural benefit, and have been bred or altered by humans for some reason.
In short, there is a zoological definition of subspecies set out in ICZN. This definition requires viable interbreeding among subspecies belonging to the same species. The term applies to individuals, or groups, as the context dictates. Analogous terms of subspecies are applied (adapted?) to other realms of biology, such as botany, microbiology and virology, but the definitions are slightly different, but consistent within the branch of biology (eg, viruses can't breed so they don't fit the ICZN definition, but the term applies). Ssp can also be qualitatively used to describe an unknown subset of a species (I've seen this used in microbiology mostly).
Crosses/hybrids are indicated with the "x" in the nomenclature. Since I found this confusing, I'm copying from Wikipedia.
From a taxonomic perspective, hybrid refers to offspring resulting
from the interbreeding between two animals or plants of different
Hybrids between different subspecies within a species
(such as between the Bengal tiger and Siberian tiger) are known as
intra-specific hybrids. Hybrids between different species within the
same genus (such as between lions and tigers) are sometimes known as
interspecific hybrids or crosses. Hybrids between different genera
(such as between sheep and goats) are known as intergeneric hybrids.
The second type of hybrid consists of crosses between populations,
breeds or cultivars within a single species. This meaning is often
used in plant and animal breeding, where hybrids are commonly produced
and selected because they have desirable characteristics not found or
inconsistently present in the parent individuals or populations. This
flow of genetic material between populations or races is often called
There are some horticultural examples of crosses in which an example of interspecific and intergeneric hybrids, and others, are shown.