(1) What is Online LED Drivers and Offline LED Drivers?
(2) What is isolated and non-isolated LED drivers?
(3) What is the difference between LED drivers and SMPS?
(3) your LED driver is just a special purpose SMPS. Where most SMPS regulate voltage and current, the LED driver just regulates current, and generates whatever voltage (up to a point) it needs to turn the LEDs on to pass that current through them.
On line / off line: On line input is 110VAC or 220VAC while off line is 12V or 24V or 1.4V
Isolated / non isolated: A non isolated, the LED is directly connected to one lead of the power line. Isolated, you can touch the LED and not get shocked. Has a transformer!