Original: It is distinguished from a shrub by its ground-hugging stems and lower height, with overwintering perennial woody growth typically less than 10 20 cm tall, or by being only weakly woody and/or persisting only for a few years.
Simplified: Gardeners use the word to distinguished plants from a shrub that have lower height, typically less than 10 20 cm tall, or that are only weakly woody and/or persist only for a few years.