DiY tinted moisturizer and eye primer?

[stylishes]

so i was watching videos on youtube on diy (do it yourself) and they used the same things to make tinted moisturizer and eye primer and i am confused because obviously these are different things. Tinted moisturizer is kind of like a foundation but way lighter and eye primer is a base for your eye shadow so how can they contain the same things? the people in the videos use lotion and foundation/concealer for both DiY's .. so can someone explain this to me how can they be made of the same things but suppose to do different things.. if that's the case i am going to start using my tinted moisturizer as an eye primer lol