Try to ignore the negativity mate.
there are two (main) types of marker available, Electronic and Mechanical.
A mechanical Marker runs completely off Air (weather it be CO2 or Compressed Air), ie the operation of the marker runs off a series of springs, sears, valves (< Correct if wrong).
On the other hand, you sir have brought an electronic marker. These require a battery in order to run the circuit board inside the marker (the circuit board is responsible for the management of the markers functions for the most part) The circuit board essentially replaces the 'mechanical or moving parts parts' that do the same thing on a mechanical marker, the board also allows for the use of a host of firing modes, and other useful features otherwise not available on a mechanical marker (like a eye vision system, dwell, etc etc)
Some consider a mechanical marker better for new comers to the sport. Simply because they are considered easier to use, understand and to learn from. Once familiar with that they normally wish to make the move to electronic markers.
ps. if any of the above is incorrect, feel free to make corrections. Its like explaining something you instinctively know but cannot explain
Anyway, a battery is absolutely 100% required for your marker to operate fella, Best of luck
-Sugz