Often wrongly described as Geraniums, true Pelargonium come from South Africa. There are 6 distinct groups:
Regal: Bushy evergreen perennials and shrubs with rounded leaves sometimes lobed or partially toothed, producing single rarely double flowers in shades of mauve, pink, purple or white grown for outdoor or indoor display

Angel: Similar to regals, but more compact and bushy. Mostly derived from P. crispum

Ivy-leaved: Trailing evergreen perennials with stiff fleshy leaves and single or double flowers used for hanging baskets or containers

Zonal: These are mainly derived from P. inquinans and P. zonale. Upright, bushy, succulent-stemmed perennials grown for their single or double flowers. Some have attractive foliage. This type is most commonly used for bedding displays

Scented-leaved: Shrubby evergreen perennials and shrubs, which are mainly cultivated for their scented and often distinctly lobed, toothed or incised or variegated leaves

Unique: Shrubby evergreen perennials that do not fall into the above categories