It's actually quite simple, and the answer is in the question!
A Blanc de Blancs Champagne is actually a white wine made exclusively from white grapes. 100% Chardonnay, for example. Generally, the characteristics of this wine are great freshness and minerality, notes of citrus (lemon, grapefruit), white flowers (hawthorn, acacia), green apple, and sometimes a chalky touch characteristic of the Côte des Blancs terroirs. With age, it can develop aromas of brioche, honey, and almonds.
A Blanc de Noirs Champagne is a white wine made exclusively from black grapes. Pinot Noir and/or Pinot Meunier. The style is more powerful, full-bodied, and vinous. Pinot Noir brings structure, power, and notes of red and black fruits (cherry, blackberry). Pinot Meunier is smoother, fruitier, and rounder. These wines often develop aromas of ripe fruit, mirabelle plum, quince, and even a hint of hazelnut with toasted and spicy notes with age.
Not all champagnes are either Blanc de Blancs or Blanc de Noirs ! For example, our Brut Grande Réserve is a blend of three grape varieties: Chardonnay, Pinot Noir, and Meunier.
You probably have other questions; here are our answers in the following links:
What is the difference between a brut and a demi-sec?
What is the difference between a Non Vintage and a Vintage Champagne ?