When I add a subdivision modifier and smooth my model I get artifacts. Modeling a human head. Blender 2.80 I'm new to the Blender forum and 3D modeling in general. I am using Blender 2.80 (2019-05-03). I have followed a tutorial in order to model a head. When I add a subdivision modifier and smoothing I get these strange artifacts (see pics). Has anyone seen this and would you have any idea what's happening and how to fix it and avoid it in the future? I'm not sure what I'm doing wrong. Thank you so much!

Blend file: HeadTutorial.blend Thanks again!
moonboots answered my question correctly. Shift + N is the "Make Normals Consistent" shortcut. 

Blender 2.80 Normals documentation: Normals

Here is the "fixed" model after implementing the fix:


Thanks for the help, @moonbots!