They were known as Geraniums by Botanists but the S.African frost tender
types were renamed Pelargonium in, I believe, the 1930s but in this instance
the trade always resisted changing the name, strange when they were quick to
change some Datura to Brugmansia quite recently.
Whilst the true geraniums are small hardy perennials there are three that
are quite large and spectacular and well worth growing if you can provide
the required conditions.
G. maderense for example is amazing in flower and has a strange way of
growing with the older leaves pushed hard down to the ground to buttress the
short trunk, but it isn't hardy in the UK and it's monocarpic.
G. palmatum is hardy and seeds itself around my garden (in a rather
civilised way).
G. canariensis I haven't grown yet.

Pelargonium was published in 1789 but it had been Geranium since the
1600s and the name stuck. Another change that still hasn't been
completely accepted is Hebe for Veronica.

A guy I worked for in 1969 got some G. palmatum seeds from the RHS. I
got some and they have followed me through six moves to different
places in Monterey and San Louis Obispo counties. They are quite
aggressive here and have to be pulled up before they set too much seed
or they would take over the whole yard. Actually they did take over at
the first place we grew them. Still their ferny leaves and magenta
flowers are nice in a woodland setting and I always make sure to have
some when we move.

Canariensis is a lot like a perennial palmatum and they form a trunk as
they grow. They aren't as aggressive here.

--
Prunedale California
Prunetuckey-By-The-Slough
Near Monterey Bay and Elkhorn Slough