A hair toner is used after bleaching hair to neutralize and remove brassy (yellow/orange/red) shades, keeping the blonde color intact. Wella hair toner is also used to brighten.
How to Use Toner to Remove Yellow-Bleached Hair : Hair Color & Styling Tips
Wondering how to maintain the smoothness of your white hair? This post talks about the 10 best white hair toners that can enliven your white hair.
How to Mix & Apply Toner to Brassy Hair
Depending on your undertone (especially after bleaching--hello brassy oranges and yellows) choose a toner or hair color with the correcting tone as its base.
Fact about Wella color charm toner