Dark energy and cosmic acceleration

The discovery that we live in an accelerating universe changed drastically the paradigm of physics and introduced the concept of \textit{dark energy}. In this work, we present a brief historical description of the main events related to the discovery of cosmic acceleration and the basic elements of theoretical and observational aspects of dark energy. Regarding the historical perspective, we outline some of the key milestones for tracing the journey from Einstein's proposal of the cosmological constant to the type Ia supernovae results. Conversely, on the theoretical/observational side, we begin by analyzing cosmic acceleration within the context of the standard cosmological model, i.e., in terms of the cosmological constant. In this case, we show how a positive cosmological constant drives accelerated expansion and discuss the main observational aspects, such as updated results and current cosmological tensions. We also explore alternative descriptions of dark energy, encompassing dynamic and interacting dark energy models.