If something is squishier, it is softer and easier to press down.
Squishier things might make people think of comfort, like a soft bed or a fluffy pillow.
Examples:
The sponge is squishier than the rock.
My pillow is squishier than my toy.
The squishier the bed, the better I sleep.
I like squishier bread for my sandwich.
The marshmallow is squishier than the gummy bear.
The squishier the hug, the better it feels.