Rapid advances in neurotechnology enable bidirectional communication between the nervous system and engineered devices. The precise recording and stimulation of typical target neurons by neural interfaces with adequate materials and structures can provide revolutionized medical applications, including the diagnosis and treatment of neurological disorders. Thereby, a proper understanding of the electronic device and its interfacing biological surroundings is necessary. Here, this review highlights the basic concepts of neural signaling, neural recording, and stimulation to help understand neural interfaces. Then, we summarize the considerations of the materials and introduce a variety of materials that satisfy the requirements. Furthermore, the key challenges for next-generation neural interfaces are considered, and future directions are explored based on recent studies.