Oh my... Homework... Here I go.
which type of paper is most environmentally friendly
There are two main types of "environmentally friendly".
1) The one made with already recycled paper.
2) One that is certified as environmentally friendly. The main seal I know is http://fsc.org which verifies that all the process is environmental friendly, including reforestation.
What type of paper is commonly used to print flyers
The three main categories are
a) Not coated. It is cheap but the collors are dull. For one ink flyer is fine.
b) Coated. For a full color flyer. Like the ones on a color magazine.
c) Special papers. Texturized for example.
a slight shinny finish
A glossy paper has glossy finish.
A matt has matt finish.
A satin has a slight shinny finish.
But this can be modified using a varnish.