<p>Virtual assistants (VAs) have become essential instruments in modern technology, transforming human–machine interactions across various disciplines. Their use of natural language processing, cloud, and IoT has facilitated assistance with activities from everyday conveniences to intricate decision-making in healthcare, education, and other domains. This review seeks to consolidate disparate research by offering a novel comprehensive taxonomy of virtual assistants, as well as smart speakers, as a key embodiment of VAs, highlighting their integration with IoT ecosystems and their ability to enable intuitive, multimodal interactions. This study employs a thorough literature analysis to assess diverse applications of VAs across domains, while also critically examining the challenges and limitations. By addressing these barriers and consolidating fragmented research, this study provides a unified framework for understanding VAs and their future role in fostering intelligent, inclusive ecosystems.</p>