What exactly are the differences between Master of Science and Master of Engineering?

[H X]

I am a freshman in Electrical Engineering program in United States. My main reason for asking this question can be described by the following question;

do you absolutely need Master of Science to be considered in a PhD program, or can you just have Master of Engineering as well?

I heard you need MS becuz of research aspects, but I've seen graduate schools offering MS without thesis(wonder if that's legit).
If anyone has any personal accounts to make the comparisons, that would be great.
Thank you very much to everyone in advance!