A simple explanation of the elements of a light and switch. Bare ground wires are not shown in diagram, but at both light fixture and at switch location the bare ground wires are connected together.
If using a metallic electrical box connect the bare ground to the grounding screw of box. If the switch has a grounding screw then connect to ground. Should the light fixture have a grounding screw (possibly green) or a green wire then connect to the bare ground wire and electrical box (if metallic).
The white wire from the circuit power supply cable at light fixture is a neutral wire that connects to the white wire or silver color screw of light fixture. The black of the circuit power supply cable as shown in diagram connect to the white wire of the cable going to switch. This white wire is NOT a neutral but a white being re-designated to carry a hot (live) power feed to the switch and therefore should have a piece of black electrical tape wrapped around the white wire at both the light and switch end of the wire to signify that it is a hot wire. Note however in some existing situations , there may be a white wire being used to carry a hot feed to the switch that has not be wrapped in black electrical tape.
The black wire coming back from the switch gets connected as a switched hot to the black wire or brass color screw at light.
Note that green wires, green screws, or bare wires are grounds.
In the event that an unswitched source of power is needed to continue the circuit onward from the light fixture. Then connect the onward cable to the circuit power supply cable, black to black, white to white, bare to bare (& box if metallic).
In the event that a switched source of power is needed onward (ie. another light fixture). Then connect black to black coming from switch, white to white of power supply cable, bare to bare (& box if metallic).
All wire to wire connections should have the appropriate size insulated electrical nuts over the connections.