Something I know using word never. For an example:
I never do this thing.
but I don't know what is the meaning of ever. Can you describe me both never and ever?
Never X is equivalent to not ever X with some shifting around of words.
I never was there = I was not ever there.
I never do this thing = I do not ever do this thing.
It's archaic to use ever without some negating word, so ever X is not really a commonly used "opposite" of never X.
Nothing was ever in the box (fine because of nothing)
Something was ever in the box (doesn't work)
No one ever answered the door (fine because of no one)
John ever answered the door (nope)
Using a negative word and never is a double negative and frowned upon, but you will hear it in live speech occasionally, often for emphasis.
No one never came by!