What was the role of anode in the cathode ray experiment

was the anode necessary. what was the role of it?
in my book. in the picture it says a voltage source? what really is voltage source n what does it give off??
in the picture there are two wires going from the voltage source to either end of the tube(anode and cathode). what is the voltage source giving off? (electricity, electrons protons or what?) i mean if it is giving off charged energy, then how come they just found out that there are negatively charged particle? shouldnt they already kno because there were plus and minus "things" going from the voltage source to the tube

In a cathode ray tube (crt) the cathode is heated with a filament and negatively charged electrons are released from the cathode and accelerated across the partial vacuum inside the crt, attracted towards the anode which has a large positive voltage.

This flow of electrons is called an "electric current" which completes a circuit through the voltage source via the wires you mention, and out again across the gap. Think of the voltage source as a supply of electrical "pressure" which pushes the current around the circuit, like a water pump pushing water molecules through a pipe.