Oak trees - classified as members of the genus Quercus - are acorn-producing trees that belong to the beech family. They're common all over the northern hemisphere, including here in the British Isles, with over 600 different species worldwide. Some of these species can grow to heights of around 100 feet - over 30 metres. Some keep their leaves all year (evergreen), whilst others are deciduous, losing their leaves in autumn and winter. They can live for hundreds of years.
Oaks can be identified by a set of common features. They're the shape that we all learn to draw trees - rounded leaf canopy coming down into a straight trunk. They have lobed leaves and produce acorns. The bark is ridged, and can vary from quite light brown to quite dark brown. In spring, their buds are chocolatey in colour and are small and pointy.