What do the lights on the Philips Hue Bridge mean?

The Philips Hue Bridge has 4 glowing blue lights on top, with some symbols that allude to their functions - but what do they actually mean?

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Can anyone explain this to me, why my hue bridge has a white light instead of blue. : r/Hue

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Hue Bridge - Smart Control for your Lights

Hue Bridge - Smart Control for your Lights

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Hue Bridge - Smart Control for your Lights

What do the lights on the Philips Hue Bridge mean?