Outliers, or data points significantly distant from others, can arise due to various factors such as system changes, errors, or natural deviations, and they can significantly impact machine learning models like linear and logistic regression by skewing results. Different methods exist for detecting and treating outliers, including univariate and multivariate analyses, with techniques like the Z-score method and Cook's distance offering ways to assess and address their influence. While outliers can affect both dependent and independent variables, their treatment—through either transformation or removal—can enhance model performance, especially in linear regression models. Visualizations like scatter plots and box plots are suggested for identifying outliers in smaller datasets, though advanced methods like PCA and LOF are recommended for high-dimensional data. The blog emphasizes that while removing outliers can sometimes improve model accuracy, it should be done cautiously to avoid losing valuable data variability, advocating for transformation techniques as a generally more effective approach.