Short answers, pulled from the story.
Shrubs are generally distinguished from trees by their multiple stems, which branch at or below ground level, and by their shorter height, typically less than 8 metres in botanical classification. Trees usually carry a single main trunk that rises a reasonable distance before dividing. Some species can grow as either a shrub or a small tree depending on growing conditions.
A subshrub is a small, low shrub generally less than 2 metres tall. Examples include lavender, periwinkle, and most small garden varieties of rose. The term distinguishes these compact woody plants from larger shrubs and from herbaceous plants.
Shrub lifespans vary widely by species. Some shrub species live only about five years in good conditions, while larger and more woody species can survive beyond 70 years. On average across species, shrubs die after about eight years.
Shrubification refers to the marked increase of shrublands in arctic regions observed over recent decades. Rising temperatures are a key driver, shifting plant communities toward woody shrubs and altering both plant community structure and carbon balance in these landscapes.
A shrubbery is an area of cultivated shrubs in a park or garden, also called a shrub border or shrub garden. It was a fashionable garden feature a century ago but is now somewhat less common. Rhododendrons are among the most widely cultivated shrubs, bred especially for flowering.
Tea and coffee sit on the boundary between trees and shrubs. Both are normally harvested from shrub-sized plants, but either could grow into a small tree if left without pruning or harvest. They are treated as shrub-sized crops in cultivation.