When we're building a machine learning model, it is very important that we select only those features or predictors which are necessary. Suppose we have 100 features or predictors in our dataset. That doesn't necessarily mean that we need to have all 100 features in our model. This is because not all 100 features will have significant influence on the model. But then again, this doesn't mean it will be true for all cases. It depends entirely on the data we have in hand. Here is more info about why we need feature selection. There are various ways in which you can find out which features have very less impact on the model and which ones you can remove from your