Bias & Variance in Machine Learning

Linear Regression is a machine learning algorithm that is used to predict a quantitative target, with the help of independent variables that are modeled in a linear manner, to fit a line or a plane (or hyperplane) that contains the predicted data points. For a second, let's consider this to be the best-fit line (for better understanding). So, usually, points from the training data don't really lie on the best-fit line only, and that makes perfect sense because any data isn't perfect. That is why we are making predictions in the first place, and not just plotting a random line. The linear regression line cannot be curved in order to include all the training set data points, and hence is unable to capture an accurate relationship at times.