All the world around.
It has two fundamental properties: time and space often considered as sub-properties of one space-time property.
It consists of two fundamental components: charges and fields.
The charges interact with each other through the fields.
The spatial field gradients are called forces.
The variation of charges location over time is called motion.
The variation of fields over time is called field dynamic.
The interaction between charges and field dynamic is subject to fundamental laws which is the main subject of Physics.