is material cost the same as variable cost?

No. Materials are variable, as they won't be used unless you actually produce something. (By definition of variable costs.) However, that doesn't make them the same thing, because there are variable costs that are not materials.

It's kind of how an apple is a fruit, but "apple" and "fruit" aren't the same cause there's more fruits than just apples. If you were making an apple pie, you would have to know that just any old fruit is not appropriate, right?