The number "two" has two different meanings in the Bible.
In most cases "two" indicates a joining together or unification. This is easy to see if we consider the conflicts we tend to have between our "hearts" and our "heads" – between what we want and what we know. Our "hearts" tell us that we want pie with ice cream for dinner; our "heads" tell us we should have grilled chicken and salad. If we can bring those two together and actually want what's good for us, we'll be pretty happy.
We're built that way – with our emotions balanced against our intellect – because the Lord is built that way. His essence is love itself, or Divine Love, the source of all caring, emotion and energy. It is expressed as Divine Wisdom, which gives form to that love and puts it to work, and is the source of all knowledge and reasoning. In His case the two aspects are always in conjunction, always in harmony.
It's easy also to see how that duality is reflected throughout creation: plants and animals, food and drink, silver and gold. Most importantly, it's reflected in the two genders, with women representing love and men representing wisdom. That's the underlying reason why conjunction in marriage is such a holy thing.
So when "two" is used in the Bible to indicate some sort of pairing or unity, it means a joining together.
In rare cases, however, "two" is used more purely as a number. In these cases it stands for a profane or unholy state that comes before a holy one. This is because "three" represents a state of holiness and completion (Jesus, for instance, rase from the tomb on the third day), and "two" represents the state just before it.