The power source has been upgraded to 2.5A instead of 2A, allowing the Pi to power even more powerful devices over USB ports. The Pi 3 has four built-in USB ports for connectivity to a mouse, keyboard, or anything with a USB connection. A USB hub can be used for even more connection, and it's recommended to use a powered hub to not overtax the on-board voltage regulator.
To power the Raspberry Pi 3, plug any USB power supply into the micro-USB port. The Pi 3 has no power button so it will boot when power is applied. To turn off, shut down the Pi 3, then remove power. The low-level peripherals on the Pi make it great for hardware hacking. The 0.1" spaced 40-pin GPIO header gives access to 27 GPIO, UART, I2C, SPI, 3.3 and 5V sources.