Step 1: In **trans** geometry, identical ligands are at $180^\circ$ (opposite). $[NiBr_2(PPh_3)_2]$ is square planar; "trans" means Br-Ni-Br is a straight line.
Step 2: In octahedral $[MA_3B_3]$ complexes, **meridional (mer)** means the three identical ligands occupy the vertices of a triangle that passes through the metal center (a meridian).
Step 3: In **facial (fac)**, the three ligands are on one triangular face of the octahedron.