Placing decoupling capacitors when building an Arduino PCB with Atmega328-PU
The Autodesk link explains it very well.

You should place small/fast decoupling capacitors (0.1uF) close to the power pins of your on-board ICs to deal with local spikes in power consumption of those devices. 

Place a larger/slower decoupling capacitor (1uF or larger, depending on many factors such as distance of the power supply from the board and expected power consumption) somewhere on the board to deal with varying loads and ripples in your power supply.

This has been common practice at least since I’ve started with electronics about 40 years ago (and probably much longer).