building an Arduino on a breadboard

Hello people.
Consulting the Arduino documentation (available at, I noticed that there is a 1M resistor connected to the 16MHz crystal pins.
In the examples of mounting the ATMEGA328P on protoboards that I found on the Internet, however, I never saw anyone put this 16M resistor.
Is this resistor necessary? Is it better to put it on?

Doesn’t the Uno have a resonator?