Stray Capacitance
A parallel plate capacitor is made of two metal plates facing each other. In fact two make a capacitor, we do not need the plates to be parallel, or even close to each other. Any two conductors in proximity to each other, with a potential difference between them will five rise to a capacitance. These capacitances are usually unwanted and are anyway unavoidable. The job of the designer is to minimise these so they are much smaller than any capacitance in the circuit and do not produce a signal that distorts the desired output. This is done by minimising the lengths of conducting leads and grouping components together.