LEDs are typically driven in systems where there are many LEDs in such way that you have a set of LED groups. Each of those LED groups consist of series connected LEDs plus some current limiting electronics (could be a resistor, electronic current source, switch mode power supply in current mode etc..). In simplest LED systems use several LEDs in series (the sum of their voltage drops somewhat lower than supply voltage) plus a suitable current limiting resistor which has resistance = (supply voltage - sum of LED voltage drops) / led current.
In applications where you need more LEDs than you can put in series to one LED group, you build several identical LED groups and wire them in parallel.

LEDs can be very well controlled with PWM.