The Arduino Nano 33 BLE is an evolution of the traditional Arduino Nano, but featuring a lot more powerful processor, the nRF52840 from Nordic Semiconductors, a 32-bit ARM® Cortex™-M4 CPU running at 64 MHz. This will allow you to make larger programs than with the Arduino Uno (it has 1MB of program memory, 32 times bigger), and with a lot more variables (the RAM is 128 times bigger). The main processor includes other amazing features like Bluetooth® pairing via NFC and ultra low power consumption modes.
The Nano 33 BLE comes with a 9 axis inertial measurement unit (IMU) which means that it includes an accelerometer, a gyroscope, and a magnetometer with 3-axis resolution each. This makes the Nano 33 BLE the perfect choice for more advanced robotics experiments, exercise trackers, digital compasses, etc.