A little bit about the history of the Geraniaceae genus:

The Geraniaceae family is a very diverse group of plants. Whilst one type heralds from the northern hemisphere many of the sub-groups originate from south of the equator.
The two most common, the hardy north European ‘Geranium’ and the half Hardy ‘Pelargonium’ are grown extensively in the ‘developed western world’
Whilst the common hardy Geranium is native to Europe the majority of what are botanically classed as ‘Pelargoniums’ come from South Africa. There is a great deal of confusion arising from this classification as, despite the marked difference between the two, many types of Pelargoniums are still commonly called Geraniums (see below).
When these plants first arrived in the 1600-1700’s they were considered to have a similar seeding habit to our hardy European Geraniums, hence they were originally botanically grouped with them. 
Their seeding habit though (the traditional birds beak) was common which suggested a genetic link.
Consequently Botanists created a new Genus to include all of the known groups under a heading named Geraniacea. They also named some of the section groups using Greek names after their bird beak characteristics.

Today the 4 most common groups are:

The Erodium (Herons Bill). Generally these are smaller hardy to half hardy sub shrubs that in many cases grow in a similar fashion to ground covering alpine type plants. To survive a temperate winter the majority would need a very well drained soil i.e. a rockery site. Some examples are shown opposite;

The Geranium (Cranes Bill) – this is the common north European hardy herbaceous shrub that is popular to grow in the UK. See Video HERE.

The Monsonia (Lady Ann Monson – Named after a South African Plant collector) Generally half hardy shrub like plants that have larger base originating flower sets. Their spread from South Africa has not been so prolific so is less common overseas. An example is shown opposite;

And finally… The Pelargonium (Storks Bill). 
There has been a great deal of confusion over the years about the naming of the Geranium and Pelargonium groups. This confusion originally arose out of the original botanic classification when the Pelargonium section was grouped in with the Geranium section. Whilst the re-classification (described above) set the rules straight over the years large commercial nurseries have tended to ignore it. See group section descriptions and videos HERE