Problem:

What exactly does it mean when a plant has a scientific name that specifies a variety, for example Nothofagus solandri var. cliffortioides, or when the name includes an "x", as in Populus maximowiczii Henry x trichocarpa, Populus x canadensis, or "Crataegus x macrocarpa"?
All of these species are in the USDA Plants database (of plants that occur in the US). There are > 6000 occurrences of the string " var. " ~500 occurrences of " ssp. " and only a handful occurrences of " x " in the database,

Question: Does the x indicate that a plant is a hybrid, and are the varied uses indicate a different meaning?

Question: Does the use of " var " mean that the plant is a variety?

Question: Does it mean that each of these species has been cultivated and/or bred by a human?

Question: Does "ssp" mean that the plant is distinct yet compatible with others in the species?

Question: Is there a way to identify that a plant is cultivated based on its scientific name?

Please provide all the answer for the following questions.