What is how does second-future tense differ from the first-future tense?
I don't believe those are standard grammatical terms.
I've never heard of "first-future tense" or "second-future tense." There is simple future tense ("Tomorrow, we eat pizza!"), future progressive ("We are eating pizza tomorrow."), and future perfect ("By his time tomorrow we will have eaten pizza!"), and several other constructions, but none of the books I have at hand mention a second-future tense. Is this for an English class?