Searching for smoother or rounded corners to make your object more realistic?
You can look at this guide, or you can follow these following easy steps.
You can make it in two different ways:

MODELING WITH BEVEL TOOL

This makes permanent the modification to your object. Start moving and then control it by the new panel nearby.

the more segments there are, the more rounded is the effect

You can set a material (for renders) for specific faces created with this tool (see Material index).

ADD A BEVEL CHARACTERISTIC

By acting from the properties of the element, you can always come back to modify them. Go to the Modifier properties, and click on Blender to activate the modification parameters.

Same result?

aesthetically yes! But with the first one, it is permanent (but you can modify material of some faces) and with the second one you can always come back to your choices!