What is accretion, and how does it relate to the formation of the Earth?
Accretion is a process in which matter comes together and leads to gradual increase in the size of an object
In space , what pulls the matter together is gravitational force.
So , how it is related to earth's formation is that when the Sun was born it had spawned a large amount of rocks and cosmic floatsam.
All these rocks and floatsam gradually started accumulating or accreting onto each other.
Slowly but steadily , they accumulated onto each other to such an extent that it reached a certain size.
Over the course of time , this lump of accreted material from the birth of solar system evolved into our planet , Earth