Can somebody explain a variable for me

I was looking at a script i found online and this script has to do with the collision of the character but there is a part I dont understand. More specifically I cant figure out how the value of this variable is calculated

public class Collision : MonoBehaviour
{

    [Header("Layers")]
    public LayerMask groundLayer;

    [Space]

    public bool onGround;
    public bool onWall;
    public bool onRightWall;
    public bool onLeftWall;
    public int wallSide;

    [Space]

    [Header("Collision")]

    public float collisionRadius = 0.25f;
    public Vector2 bottomOffset, rightOffset, leftOffset;
    private Color debugCollisionColor = Color.red;

    // Start is called before the first frame update
    void Start()
    {

    }

    // Update is called once per frame
    void Update()
    {
        onGround = Physics2D.OverlapCircle((Vector2)transform.position + bottomOffset, collisionRadius, groundLayer);
        onWall = Physics2D.OverlapCircle((Vector2)transform.position + rightOffset, collisionRadius, groundLayer)
            || Physics2D.OverlapCircle((Vector2)transform.position + leftOffset, collisionRadius, groundLayer);

        onRightWall = Physics2D.OverlapCircle((Vector2)transform.position + rightOffset, collisionRadius, groundLayer);
        onLeftWall = Physics2D.OverlapCircle((Vector2)transform.position + leftOffset, collisionRadius, groundLayer);

        wallSide = onRightWall ? -1 : 1;
    }
}

Can somebody please explain what the “public LayerMask groundLayer;” does in this script?

Hi @freyescicero19 ,

The groundLayer is passed as the layerMask to the Physics2D.OverlapCircle method.

The purpose of such an argument is to filter the objects that are only in a specific layer, in your case the groundLayer.

You can find more information about it here: Unity - Scripting API: Physics2D.OverlapCircle

I hope this helps you to understand better the code!