The Poincaré Group is 10 mathematical transformations that can be applied to different coordinates of the space-time graph (x, y, z, ct), but does not affect the "spacetime interval". The "spacetime interval" is roughly the 4-D equivalent of 3-D "distance".
These transformations are:
Spatial translations:
Time Translations:
Spatial Rotations:
Lorentzian Transformations: