Logistic Regression is a variant of linear regression where the target variable is categorical, i.e. it takes one out of a few possible discrete values. Each of these values is called a label. Don't be confused by the name logistic regression, it's a classification algorithm.
In particular, we can use logistic regression for binary classification (two labels). For example, we might want to predict whether or not a person has diabetes, or whether or not an email is spam.