What does "Seven pairs" mean in Genesis 7:2-3?

Q: Growing up, I learned that Noah brought in the animals "two by two," but Genesis 7:2 talks about "seven pairs."How do you explain this?

A: That's a great question, and it's one that gets a little bit into Hebrew phrases like "seven sevens" that we also see echoed in the book of Daniel and some of Jesus' teaching. Here are a few perspectives:

1.  What I Say: Genesis 6:19-20 is a general command of "two of every sort" and Genesis 7:2 is more specific within that general command: 
   "Seven pairs of all clean animals, the male and his mate, and a pair of the animals that are not clean, the male and his mate, and seven pairs of the birds of the heavens also"
   In other words, "Hey, Noah, bring 2 of everything, and in regard to clean animals, unclean animals, and birds, do this specifically..." The Hebrew is a little difficult, because it says "sibah, sibah" (seven sevens) and not seven pairs. Elsewhere, like Daniel's "seventy-sevens" or when Jesus' forgive others "seventy times seven," those numbers indicate completion or totality rather than specific integers.
2. What GotQuestions Says: The Hebrew phrase translated “seven pairs” literally means “seven sevens,” so there is some question as to whether Noah took seven specimens of each “clean” species (three pairs and an extra) or seven pairs. Either way, he was told to take more clean animals than unclean on the ark. Only the unclean animals came in pairs https://www.gotquestions.org/animals-clean-unclean.html
3. What the Christian Apologetics & Research Ministry Says: "Genesis 6:19-20 simply instructs Noah to preserve two of every kind. Genesis 7:2-3 is additional information where seven of the clean animals were to be taken and two of every other kind. The reason for this is that the extra animals were for sacrifice. " https://carm.org/how-many-kinds-did-noah-bring-ark-two-or-seven
4. What "Ockham's Razor" Might Say: The simple answer is usually the best. The overall command was a general "two of every sort" and then God explained it more specifically in regard to certain kinds of animals.