Seek to understand what the dot space group symbols mean and how to read them?

The first P stands for the lattice type, which is represented as a primitive lattice; the second one is 63/m,which means that there is a spiral axis of 63 in the direction of the c-axis, and there is also a plane of symmetry perpendicular to the spiral axis, the third position means that there is a plane of symmetry perpendicular to the C-axis in the direction of the a-direction, and the fourth one represents the direction perpendicular to the C-axis, and making an angle of 120 degrees with the a-axis, there is a C-slip surface (which is slipped along the c-axis).