what does scree plot tell you code example

Example: scree plot

from matplotlib import pyplot as plt
from sklearn.decomposition import PCA
import seaborn as sns
import pandas as pd

pca = PCA.fit(X_train)
            
df_var_explained = pd.DataFrame(pca.explained_variance_ratio_)

plt.figure(figsize=(20, 20))

sns.barplot(x=columns,y=pca.explained_variance_ratio_, 
            data=df_var_explained, color="c");