English: "Seven days" — It was taught: One may leave one sukkah for another and may build a sukkah during Chol HaMoed. What is the reason? Because it is written "the festival of Sukkos you shall make for yourself seven days"—thus the Merciful One says: make a sukkah during the festival.
On the daf / in context: The obligation to dwell in a sukkah continues throughout the seven days, and a new sukkah may be constructed even after the festival has begun.
Type of Learning
Derash on the verse (Sukkah) — one may switch sukkos and build during Chol HaMoed.
What Is Learned
One may move from one sukkah to another during the festival and may even construct a new sukkah during Chol HaMoed.