Evaluation in machine learning is the process of assessing a model's performance on unseen data to determine its ability to generalize beyond the training set. This typically involves using a separate test set and various metrics like accuracy or F1-score to measure how well the model performs on new data, ensuring it isn't overfitting or underfitting.
In federated learning, evaluation (or distributed evaluation) refers to the process of assessing a model's performance across multiple clients, such as devices or data centers. Each client evaluates the model locally using its own data and then sends the results to the server, which aggregates all the evaluation outcomes. This process allows for understanding how well the model generalizes to different data distributions without centralizing sensitive data.