Anode, Cathode and Membrane
Anode
The word anode comes from the Greek άνοδος = 'going up'.
An anode is the positive electrode in an electrolytic system or circuit. So the path through which the electrons move out of an electrolyte solution.
In electrochemistry, the anode is where oxidation occurs and is also the negative discharge plate in an electrochemical cell. In electronic circuits such as a cathode ray tube or a diode, the anode is the positive plate.
In solution negatively charged particles, anions, flow to the anode. In vacuum tubes or circuits electrons flow to the anode.
An anode is the opposite to a cathode. In charge mode the flow reverses and this plate becomes the cathode.
Cathode
The word cathode comes from the Greek κάθοδος = 'going down'
A cathode is the electrode at which electrons go into a cell, tube or diode whether driven externally or internally. The other charged electrode in the same cell or device is the anode.
Membrane
A membrane is a thin, typically planar structure or material that separates two environments. Because it sits between environments or phases and has a finite volume, it can be referred to as an interphase rather than an interface. Membranes selectively control mass transport between the phases or environments.