What is the difference between live and switch live?

120vac circuits:

N = neutral (white wire in the USA)

E = earth (green or bare wire in the USA)

S = switched (red wire in the USA) 120vac only when switched on

L = line (black wire in the USA) 120vac on all the time

Connect the S wire on the light fixture to the live wire from the ceiling (presuming that live wire is switched from a wall switch). If the live wire on the ceiling is not switched from a wall switch, your light fixture will be on all the time. Check to see if that wire is controlled by a wall switch. If not, you can buy a wireless wall switch and receiver to control the light fixture (been there, done that with my ceiling light & fan).

assuming it is on a switch, the switch live one does. the Live line is used when the fitting has a radio control mechanism [dimmer]

your multimeter can test the lines to discover for certain which ones are live and when [switch position]

Switch live means that the wire is live (hot) when the wall switch is turned on.

Live means that the wire is always on!

If you have a wall switch to control the light then:

On your light fixture: N = neutral, E = earth (ground), S = switch live (connect to this one with your wire on the ceiling)

If you do not have a wall switch to control the light and this fixture does not utilize the live wire in it, then you have the wrong type of fixture for your application. You need a light that has the switch installed on it!

how many wires of which colours do you have coming out of the ceiling?

If you have a single wires with 3 cores (brown/red), (black/blue) and bare earth then the "live" is a switched live, and the s on your light is unused