Help with a collider script

Questions:

1. In this script, why are we doing the raycasts and collider size and center initialization under the for loop?

2. For float y, what does " s.y/2 * dir; " actually mean? Similarly for float x in the left and right collisions

Note: DeltaY is equal to my jump height -= gravity * Time.deltaTime

DeltaX is equal to the direction the player is going in and his speed.

 using UnityEngine;
 using System.Collections;
 
 
 [RequireComponent (typeof(BoxCollider))]
 public class PlayerPhysics : MonoBehaviour {
     
     public LayerMask collisionMask;
 
     private BoxCollider collider;
     private Vector3 s;
     private Vector3 c;
     
     private float skin = .005f;
     
     [HideInInspector]
     public bool grounded;
     [HideInInspector]
     public bool movementStopped;
     
     Ray ray;
     RaycastHit hit;
     
     void Start() {
         collider = GetComponent<BoxCollider>();
         s = collider.size;
         c = collider.center;
     }
 
     public void Move(Vector2 moveAmount) {
         
         float deltaY = moveAmount.y;
         float deltaX = moveAmount.x;
         Vector2 p = transform.position;
         
         // Check collisions above and below
         grounded = false;
         
         for (int i = 0; i<3; i ++) {
             float dir = Mathf.Sign(deltaY);
             float x = (p.x + c.x - s.x/2) + s.x/2 * i; // Left, centre and then rightmost point of collider
             float y = p.y + c.y + s.y/2 * dir; // Bottom of collider
             
             ray = new Ray(new Vector2(x,y), new Vector2(0,dir));
             Debug.DrawRay(ray.origin,ray.direction);
             
             if (Physics.Raycast(ray,out hit,Mathf.Abs(deltaY) + skin,collisionMask)) {
                 // Get Distance between player and ground
                 float dst = Vector3.Distance (ray.origin, hit.point);
                 
                 // Stop player's downwards movement after coming within skin width of a collider
                 if (dst > skin) {
                     deltaY = dst * dir - skin * dir;
                 }
                 else {
                     deltaY = 0;
                 }
                 
                 grounded = true;
                 
                 break;
                 
             }
         }
         
         
         // Check collisions left and right
         movementStopped = false;
         for (int i = 0; i<3; i ++) {
             float dir = Mathf.Sign(deltaX);
             float x = p.x + c.x + s.x/2 * dir;
             float y = p.y + c.y - s.y/2 + s.y/2 * i;
             
             ray = new Ray(new Vector2(x,y), new Vector2(dir,0));
             Debug.DrawRay(ray.origin,ray.direction);
             
             if (Physics.Raycast(ray,out hit,Mathf.Abs(deltaX) + skin,collisionMask)) {
                 // Get Distance between player and ground
                 float dst = Vector3.Distance (ray.origin, hit.point);
                 
                 // Stop player's downwards movement after coming within skin width of a collider
                 if (dst > skin) {
                     deltaX = dst * dir - skin * dir;
                 }
                 else {
                     deltaX = 0;
                 }
                 
                 movementStopped = true;
                 break;
                 
             }
         }
         
         
     
         
         Vector2 finalTransform = new Vector2(deltaX,deltaY);
         
         transform.Translate(finalTransform);
     }
     
 }