The purpose of the choke is to provide a very high voltage initially between the filaments (across the two ends of the tube light). The choke serves the purpose of stabilizing the electric flow of current in the fluorescent tube.
Without a choke, the current would keep increasing without any limitation until it destroys the fluorescent tube. The function of the choke is to provide a high voltage enough for ionization to take place in a tube light and after establishment and sustenance of ionization, limit the voltage across the tube. That is the reason why a tube fuses when the choke is shorted.
Again, once the gas in the tube is ionized the choke provides a low voltage. A choke is a coil of wire. Fluorescent tubes/lamps are filled with mercury vapor. They use an electric charge to excite mercury atoms in order to produce ultraviolet light. A glow starter or commonly known as a starter is used in the tube light circuit to provide an initial current to the filaments of the tube light.
The choke, or inductor when used in fluorescent lamps serves as an impedance, limiting the current through the lamp. Often the choke is really a transformer in addition to being a current limiting device, with a low voltage tap used to heat the cathodes in a fluorescent lamp. An inductor can serve as a current-limiting device with very low losses compared to a resistor.
Without a choke maximum current flows in the fluorescent lamp, and a choke (which is an inductor) stores the current in the form of charge and reduces the value of maximum current, and helps with starting, without a choke, the lamps may get fused or never starts.