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photon has rest mass zero ... it has some mass during motion ...
A photon has mass, irrespective of its state of motion ... but the mass is relatively negligible. so, in other words.. the light doesn't itself means photons.. cause light is a electromagnetic thing that comes from this photon particle..
when the so called black hole's gravity makes the source of light to bend it towards (as they say so) so does the emission of light seems to be bend.
It's actually more subtle than that... Photons are, as far as physicists know, massless particles (m=0). They have an associates energy and momentum though, but these are relativistic properties, not like p=mv or K=1/2mv^2. If you read Prof Shankar's chapter on relativity he explains this well.
Anyway, to cut a long story short, you need general relativity to explain why gravity bends light. Gravity actually BENDS SPACE so that light naturally travels along lines that appear 'curved'. So even a particle with no mass has to follow these lines (called geodesics). Check out this youtube vid it's mindbendingly awesome: https://www.youtube.com/watch?v=vNaEBbFbvcY