Help w. toner.

I have naturally dark brown hair which was dyed and highlighed a red color about 6 months ago.

I have 2 questions. First, I want to try to "tone" the hair to a light brown and also get rid of as much red as possible. I am thinking of using the loreal creme hair highligher (the one for colored hair), and then doing something to ''tone'' it to more of an light ash brown. Would this work?

My 2nd question is this... what is a toner? I cannot figure out what to get to tone it after the highlights? Is a toner the same as a semi-permanent color, like natural instincts? or is there something called ''toner'' that I am supposed to use.. and if so, where can I buy it?

Thanks for any help...