Whats the use of channel on side of blade?

[James 99]

Some knife also have holes on these channels or fuller. Are these related to similar use as nobbe trier or reduce friction when slicing.

 

[CWL]

The fuller is there to reduce weight of the blade or sword. Some can reduce weight by almost 1/3.

Some are there for cosmetic purposes.

Kitchen knives can have Granton Edges, which are perpendicular to the edge. These serve to prevent food from clinging to blade when slicing.

 

[JBC6650]

Fuller article, https://en.wikipedia.org/wiki/Fuller_(weapon)?wprov=sfla1

GoogleFu similar to Kung Fu but with a keyboard

 

[Tony_A]

These serve to prevent food from clinging to blade when slicing.

This is incorrect. On a real, Granton brand knife, the scallops extend right into the edge itself and are there to make the edge flow in a wavy pattern than lets it cut better--sort of like left/right serration instead of up/down. All other "fake" Granton scallops are placed too far up and don't do this. They are mostly there for marketing B.S. about food sticking. see pics:

 

[DangerZone98]

Reduces weight on the blade and shifts the balance slightly towards the handle. Personally, I love it on my kukri.

 

[James 99]

Channel parallel to edge might add some strength to it, preventing bending.
like plain sheet can be bent, but wave or channel sheet would not bend easily.

How effective the design may be, everything sticks while cutting thick block of home made hung cheese.