“Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house.”Henri Poincaré · Science and Hypothesis · 1902
Geometry is a practical convention, not an absolute truth, chosen to simplify calculations.
Poincaré showed you can describe the same world using different geometries, just like you can map the same city on a flat sheet or on a globe. We pick ordinary geometry not because it is the only true one, but because it makes calculations simplest. The choice matters, even if invisible.
Why it matters This idea helped Einstein, a few years later, to think beyond ordinary geometry.