What does "else" mean in "if A then B else C" ?

I have thought it for a long time. Maybe it goes this way:

If A is true, then perform operation B. Otherwise, perform operation C.

In another words: "If the logic A then B is not true, then C happens"

Am I right?

Thank you MrP.

I didn’t see your answer until just now.

But I still feel it should like this:  "If the logic A then B is not true, then C happens"

See this example:

If I'm a human being, then I'll metabolize, else I'm frozen under a certain degree.

If "then" & "else" in the underlined sentence are not correctly used, which words should replace them to express the relevant logic?

[Well, maybe “A then B else C” is beyond my intelligence. ]

I've learned it by heart.

Thank you very very much!