The Teensy is a dev board with many interesting features in a minimal package. The only thing that's needed to program it a standard micro USB cable and a computer with a USB port.
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Pro Very easy to set up, even for beginners
The Teensy board is easy to set-up and start using with Teensyduino. Even beginners will have no trouble doing it.
Con Additional hardware is needed to connect to peripherals that are not 3.3V
This board only has 3.3V outputs, which is unsuitable to interact with several peripherals, which are either 5V or 10V. To connect to those, you need to get additional hardware.