Actuators are devices that act with the physical world based on the input received and carry out the required action. The action can be a motion, lighting, emitting sound, controlling power, etc. An example would be the connected door locks, which can be controlled (locked or unlocked) using remote control device and the actuator being responsible for controlling the movement of the lock motor.
Radio Frequency Identification (RFID) tags are smart barcodes that identify the device or a product and works in conjunction with the RFID reader to track the product information and send it across the network. These tags are attached to the products, and the reader scans the tag and extracts the product information and sends the data over the network or the cloud, which can then be further analyzed in real-time or offline. The concept also works on radio frequencies. Manufacturing, retail, and supply chain industries have long started using this concept. Even in automotive industry, vehicles are tracked with RFID during the inspection process. The concept is also making its mark in aviation and healthcare and many more industries. Near Field Communication (NFC) enables devices to communicate with each other over shorter radio frequencies. It works more like RFID, but the device with NFC protocol can act both as a reader and a tag and therefore it can also be used as a two-way communication. The ideal use case for NFC is the contactless payments where one can use a NFC enabled Smartphone and tap it to the payment terminal device to make the payment. Your card details are securely stored in the mobile and read by the payment terminal device. Both your Smartphone and the payment terminal use NFC to communicate with each other.
Beacons are another form of tagged devices that transmit signals or broadcast its location information using Bluetooth LE to the nearby Bluetooth enabled device. A smartphone can detect the beacon device and trigger an application to perform some contextual function. For example, you enter a retail store with a beacon installed denim department, and your smartphone detects the beacon signal and launches a beacon-enabled app that shows you the list of jeans brands available in the department. The communication happens on low radio frequency using Bluetooth LE or Smart Bluetooth that consumes less energy.
Apart from real life industry devices, there also exists devices to prototype or test your IoT use cases. These are controller boards itself. Some of such known devices are Arduino, Raspberry Pi, Intel Galileo, Intel Edison Board, BeagleBone, etc. Using these boards, you can create a small prototype to demonstrate the working of IoT sitting at home. The board enables you to connect to different sensors and actuators and provides network ports for internet connectivity. The ready availability of these devices makes it an ideal choice of prototyping, but these devices can also be used to build commercially connected products.