The Model Overview plot shows the explained variance of a model. For PCA, the red bars represent R2X_cum, i.e. the cumulative variance explained by the model. The blue bars represent Q2X_cum, i.e. the cumulative cross-validated variance explained by the model. For PLS, the red and blue bars represent R2Y_cum and Q2Y_cum respectively. Thus, the model overview shows variance in Y instead of X.

The user can easily add or remove components from the Model Overview plot by right-clicking on the window: