A classifier maps an input to a fixed set of labels.  The different kinds of classifiers include:

🟠 Binary Classification: email ∈ {spam, not spam}
🟠 Multiclass Classification: text ∈ {positive, neutral, negative}
🟠 Multilabel Classification: movie ⊆ {action, horror, comedy, romance, fantasy, thriller}

It works by encoding the input into a vector either through hand-build features like logistic regression or a learned encoder like CNN or BERT.  It then projects that vector to K scores (logits) with a linear layer and applies a softmax/sigmoid function to turn the scores into probabilities and takes the vector with the highest probability. (1/3)🧵