I'm trying to understand the concept of "light as waves",

As far as I know,   "wave is a disturbance in a medium" , to me it seems like wave is not an object, but it is a phenomenon.

So if light is a wave, does that mean a light is just a disturbance through medium?

 

I'm lost

16 minutes ago, Lizwi said:

As far as I know,   "wave is a disturbance in a medium" , to me it seems like wave is not an object, but it is a phenomenon.

I would say it is a mathematical description of the way the electric and magnetic fields vary regularly in a light wave. (So, yes, "phenomenon" might be the better word; definitely not an object.)

16 minutes ago, Lizwi said:

So if light is a wave, does that mean a light is just a disturbance through medium?

No. (Unless you count the oscillating electric and magnetic fields that make up the light wave as the medium.)

Just because most waves we are familiar with exist in a medium, doesn't mean that light does.

Does Huygen's principle apply to the light?

Yes: http://farside.ph.utexas.edu/teaching/302l/lectures/node150.html

1 hour ago, Lizwi said:

 to me it seems like wave is not an object, but it is a phenomenon.

That's fair. It's a particular kind (or class) of oscillatory behavior.