What does your hair look like when you get it glossed?

I want to do something different to my hair to make it look really pretty for the summer. My mom says that she started out just getting her hair glossed when she was my age. What does glossed hair look like? Will it do anything to my hair since it hasn't been dyed or highlighted? How much does it generally cost? Will my hair look different if I get it glossed?What does your hair look like when you get it glossed?
oily and greasy

medium length hair