Dark shade after connecting faces

Hi guys.
I’m obviously new here.
Can someone explain me why on earth this part become darker after connecting faces together?
Thanks for your answer

check the normals and manually correct if necessary

or add some verts smooth

happy bl

Yip, as @RickyBlender said it’s probably the normals. Go into Edit mode. Hit A to select everything and then Ctrl+N to recalculate the normals (Shift+N if you are in 2.8). If that doesn’t fix it straight away check in wireframe mode (Z) that there are no edges or faces inside the mesh that shouldn’t be there. Where the handle joins to the cup might be where an interior face has been formed or left behind.

Thanks guys, really appreciated.