I don't work with any AC LED's besides those made as a replacement for screw in light bulbs so IDK how these really work.

What I'm wondering is if LED's blink when powered by a DC power source and if they always blink or if there are applications where the light stays on constantly like in a flashlight or something as I recall seeing many circuits where the LED is driven straight from a DC power source so I can't see how it would be able to blink at XX speed.

Now I have seen LED DC drivers which I really don't understand but I think they take the DC current and pulse it at XX frequency. When and why would you need a driver for LED's vs not needing one?

As far as AC, I know many use a driver, which I guess is basically a full wave rectifier (or possibly 1/2 wave for less voltage??) to give the LED a DC source. Even in this I don't see why it would need to "strobe" with the frequency.

So why do LED's need to strobe, do all of them or just some of them?

An example of a driverless LED are the small 3-5mm LED's that are like a little bulb - the ones often used in electronics like TV's to show the power is on (for the last 20+ years or so at least, maybe they have diff ones more recently).

 

What I'm wondering is if LED's blink when powered by a DC power source and if they always blink or if there are applications where the light stays on constantly like in a flashlight or something as I recall seeing many circuits where the LED is driven straight from a DC power source so I can't see how it would be able to blink at XX speed.

Simple LED circuits do not cause the LED to blink. They run fine on a steady, regulated DC current.

Now I have seen LED DC drivers which I really don't understand but I think they take the DC current and pulse it at XX frequency. When and why would you need a driver for LED's vs not needing one?

The reason to pulse the current is to enable dimming. A PWM (pulse width modulation) dimmer is like flipping a light switch on and off very quickly. The brightness perceived by your eyes then just depends on the percent of the time that the switch is on (the duty cycle). It switches so quickly that you cannot see it flicker and you see only the average brightness.

Why not just supply less current and leave it "on" continuously? The electronics are more efficient when they're either fully on or fully off. Power is wasted in between. So flashing quickly is a way to get much higher efficiency using a very simple circuit.

As far as AC, I know many use a driver, which I guess is basically a full wave rectifier (or possibly 1/2 wave for less voltage??) to give the LED a DC source. Even in this I don't see why it would need to "strobe" with the frequency.

Same as above. An LED generally needs DC or pulsed DC. True AC can be used but is more challenging to avoid damaging the LEDs.

So why do LED's need to strobe, do all of them or just some of them?

The LED itself has no need to be pulsed. They're pulsed as a practical matter to achieve other goals.

 

What I'm wondering is if LED's blink when powered by a DC power source and if they always blink or if there are applications where the light stays on constantly like in a flashlight or something as I recall seeing many circuits where the LED is driven straight from a DC power source so I can't see how it would be able to blink at XX speed.

LEDs require additional circuitry to blink.

Jameco sells these for a nickel each in qty 10-100:

The resistor is for current limiting, an integrated circuit in the encapsulation does the blinking.

I picked up some freebies at a Maker Faire that blink in RGB.