Why SKSpriteNode node.frame.size.width is smaller than node.size.width?

Why SKSpriteNode node.frame.size.width is smaller than node.size.width ?
Here is example code ,probably you will need to insert your own image

- (void)DrawRect:(SKSpriteNode *)node
{
SKShapeNode *rect = [[SKShapeNode alloc] init];

CGMutablePathRef myPath = CGPathCreateMutable();
CGPathAddRect(myPath, nil, node.frame);
rect.path = myPath;
rect.lineWidth = 1;

rect.strokeColor = [SKColor whiteColor];
rect.glowWidth = 0;
[self addChild:rect];
}

//here draw the sprite

-(void) DrawSpriteNode
{
SKTextureAtlas *atlas = [SKTextureAtlas atlasNamed:@"character"];
SKSpriteNode* node = (SKSpriteNode *)[SKSpriteNode spriteNodeWithTexture:[atlas         textureNamed:@"testimage.png"]];

node.position = CGPointMake(self.anchorPoint.x, self.anchorPoint.y);
NSLog(@"node frame width x :%f",node.frame.size.width);
NSLog(@"node frame height y :%f",node.frame.size.height);
NSLog(@"node width y :%f",node.size.width);
NSLog(@"node height y :%f",node.size.height);

node.anchorPoint = CGPointMake(0.5, 0.5);
[self DrawRect: node];
[self addChild:node];
}