Are MacBooks much lighter than normal laptops, eg. From HP, DELL or Lenovo?
No, why should you
The components are the same
I think the pages say how much they weigh, just look. MacBooks are no longer there, only Air and Pro. They are undoubtedly very light, will hardly find something easier.
A recent Macbook Pro 15.4 "weighs 1.83kg, a gigabyte of Aero weighs 170g more, a Dell XPS 15 weighs 30g less.
A current MacBook Air 13.3 "weighs 1.25kg, a Surface Laptop 1.28kg, an EliteBook 0.99kg.
So no, Macbooks are as heavy as more or less comparable laptops from other manufacturers.