Recurrent Neural Networks (RNNs) are a class of artificial neural networks designed for processing sequences of data by introducing cycles in the network architecture. This unique structure allows RNNs to maintain a form of memory, making them especially useful for tasks involving time-series data, such as speech recognition and natural language processing. RNNs can learn patterns over time, which makes them a vital tool in the intersection of artificial intelligence and big data applications, particularly in healthcare where sequential data analysis is critical.