Raspberry Pi (referred as RPi or RPI) and its clones i.e. Orange Pi, Banana Pi, are the class of devices located somewhere between low constraint IoT boards and regular PC/Mac machines. Those devices technically origin from smartphones and are far away from energy-efficient IoT solutions powered by a single battery that lasts for weeks or even years. They need DC current (usually 5-12V and about 2-3W total, with external power adapter) but still far less than even most efficient notebooks or PCs. They also use an operating system booted from storage like regular PC computers - usually from flashed MicroSD card or embedded eMMC flash. The OS is mostly Linux based but there do exist Microsoft Windows for certified Raspberry Pi devices. This is how this class of devices differ from i.e. Arduino, where software is in SoC model. The RPi and clones are holding one-board solution that includes a processor, memory, storage slot, USB and networking. Many devices also offer hardware-based graphics acceleration, usually integrated with the processor. Some devices like Orange Pi frequently offer integrated flash for OS storage so you do not necessarily need to boot and use external flash. What is pretty similar to the low-power, constrained IoT boards is RPi and clones offer GPIO and you do can connect various sensors and expansion boards (called here “hats”).