This is a simple PCB for a DIY programmer board that connects an Arduino Nano with an ATtiny85 to allow for programming of the ATtiny85 using the Arduino as ISP (in-system programmer). 

After assembling it, connect the Arduino to your PC, then select the Arduino Nano as your board and upload the "ArduinoISP" sketch from the example sketches of the Arduino IDE. After it is done uploading, select the ATtiny85 as your board (you need to install it in the IDE by pasting this link in "Additional Boards Manager URLs" under File -> Preferences) and under Tools -> Programmer select "Arduino as ISP". Now you can upload your code to the ATtiny85.

This programmer board will also work with other 8-pin microcontrollers from the ATtiny family such as: ATtiny13, ATtiny13A, ATtiny25, ATtiny45, ATtiny85. Just make sure to select the right one when uploading your code to it.

You can also use a 3.3V version of the Arduino Nano without any changes to the hardware or programming method (apart from choosing the correct board when uploading to it).

You may need to downgrade to Arduino IDE version 1.8.18 (or lower) if you encounter the error "-fno-fat-lto-objects are supported only with linker plugin." while uploading to the ATtiny85.