Google T5 is a text-to-text transfer transformer that achieves state-of-the-art results on various natural language processing tasks. It is a pre-trained model that can be fine-tuned on specific tasks using a large text corpus. T5 provides a library for loading, preprocessing, mixing, and evaluating datasets, making it useful for training and fine-tuning models on mixtures of text-to-text tasks. It also offers modules for tokenization, metric calculation, and post-processing. T5 is designed to handle various NLP tasks and has been widely used for language generation, translation, summarization, and question-answering tasks.