Openlog is a tiny board that can store loads of data. Typically this board is used with the black box software when connected to your miniquad flight controller to log your flight data, just like a black box on a real aircraft. Openlog includes a micro SD card slot which allows you to write all of the data to an SD card (SD card not included) and you can then browse the files on your computer with a micro SD card reader. You will need to install the black box software onto this device using an FTDI adapter.
Once you have set this board up with your flight controller you can easily view and playback your flight data logs either as a CSV file, or via the black box sofware which even lets you overlay the data over your flight video. An example of this is shown below