Q:

What is the difference between normal stickers and foil stickers in CS GO?

I bought one normal sticker for pick-em challenge and it cost 0.99$. Now it shows that I can sell it at 0.78$ but in market there are few foil stickers which are more expensive (7$ to 12$) but the stickers are the same. In my case it's team envious sticker so I'm kinda confused as to what the difference between normal and foil stickers are when there are holo stickers, too.
I have searched on Google and Steam community and found that foil stickers are shiny, normal ones are blue and foil stickers show different color. But all this is just a guess and no one is sure so can some one help me to find the difference?
The links I already found about this, but are no use are these:

What's the difference between the normal, holo and foil stickers? (on Steam)
What's the difference between Holo stickers and foil stickers? (on Steam)

A:

In Counter Strike: Global Offensive there are three different types of stickers. Normal, Holo and Foil.
Rarity
These three types are also the rarity of the sticker. The rarity levels are the same as on skins in which Normal stickers are Blue (High Grade), Holo stickers Purple (Remarkable) and Foil stickers Pink (Exotic).
This means that Normal stickers are more often dropped than Foil stickers. This makes it harder to get Holo or Foil sticker.
Appearance
Of course these types have all different appearance to gain a better look on higher rarity.
Normal
Normal stickers are flat stickers that are attached on a weapon. These stickers do not have special effects except a weak glossy paper effect.

Holo
Holographic stickers are like normal stickers but they have a holographic warping effect.

Foil
Foil stickers have an embossed effect. So they do not look flat like the other two types and have a kinda 3D shape. They also have a metallic surface and shine in the light.

Keep in mind that I have simplified the complexity behind the real sticker. You can read most about the advanced specification on the official sticker guide for designers.
Price
To get the price of these stickers you have to combine the rarity and the appearance. Foil stickers are more worth because they are much harder to get and (for some people) look better than normal sticker. Keep in mind that the appearance of a sticker is fully subjectively and every person likes another style.
The main reason why Foil or Holo sticker are more worth than Normal ones is because of the rarity.
Information from counterstike wikia. Information and pictures from counterstrike blog.

