Adobe Illustrator taper lines

Hello Kirupians, I have a Adobe Illustrator question for you. I am sure that it is possible to taper lines in Illustrator, the only prblem is I can’t find any tutorials on how to effect the line width(I know how to make the whole line thicker, but have troubles making one end thicker than the other). Any suggestions on where to look? Or better yet exactly how this is done.

Any reply will be helpful.

Thanks, Odedvard