Cross validation Set - Learning curves

Hi , In week 3 , Professor explained about learning curves with different bias and models. Can you explain me why the cross and how the curves for cross validation set is determined. In the lecture professor mainly focused on Training sets

I recommend you watch the lectures again. I think he covers this.

To get information about cross validation curves, we train model on training set then we have our trained model in hand. Then we use this model to predict on cross validation set and measure how to model in performing on cross validation set using cross validation error and plot together with training error on same graph.