This is the 456th most frequent Czech word.
blesk
"Lightning."
Here, the word 'blesk' is used in its primary meaning as 'lightning', referring to the natural electrical phenomenon.
Blesk osvětlil noční oblohu.
The lightning illuminated the night sky.
In this case, 'blesk' refers to the 'flash' of a camera, an artificial light source used in photography.
Používám blesk na svém fotoaparátu pro lepší osvětlení.
I use the flash on my camera for better lighting.
Here, 'Blesk' is a proper noun and refers to the name of a Czech tabloid newspaper, which is derived from the primary meaning of the word.