  In this paper, we provide a detailed overview of the models used for
information retrieval in the first and second stages of the typical processing
chain. We discuss the current state-of-the-art models, including methods based
on terms, semantic retrieval, and neural. Additionally, we delve into the key
topics related to the learning process of these models. This way, this survey
offers a comprehensive understanding of the field and is of interest for for
researchers and practitioners entering/working in the information retrieval
domain.
