Proper method of saving

I have searched here and on the Unity Answers but I am still confused. If I am working on a project in Unity, what is the proper way to save? Now, I select ‘Save Scene’, ‘Save Project’, and ‘Save Scene’ again. Previously, I had spend the better part of a day getting everything to work while following a 3DBuzz tutorial only to discover that upon reopening Unity that ALL of those changes I had made and saved were not longer present. Could someone explain, in layman’s terms, the difference and purpose of the ‘Save Scene’ and ‘Save Project’ buttons AND when each should be used? I know that this question is exceedingly basic; however, after much searching, I still cannot find a proper explanation to this question.
Thanks,
Daryl G

I find it unlikely that any changes you saved weren’t actually saved. You probably just need to open the scene file. You use “save scene” when you want to save anything in the scene. “Save project” typically isn’t necessary since any project-type changes you make are saved when quitting anyway.

–Eric