Defining core terminology.
A zero-coupon bond is a debt security that makes zero interest payments and instead trades at a deep discount, rendering a profit at maturity, when the bond is redeemed for its full face value.
A fixed interest rate is an unchanging rate charged on a liability, such as a loan or mortgage. In the ButtonZero lending platform, it means that the user locks in their interest rate when they borrow or lend. This contrasts with "variable" interest rates that change continuously. Variable interest rates are the default for many margin lending platforms, where users must accept whatever rate change occurs.
In DeFi margin-lending platforms, users take out debt from a protocol and provide crypto assets as collateral to back the debt. However, if the debt value starts getting close to eclipsing the collateral's value, the smart contract will automatically allow third parties to bid on the collateral to cover the debt that is outstanding to the DeFi protocol. Thus, DeFi liquidation is the process by which a smart contract sells crypto assets to cover the debt. Users of ButtonZero do not need to worry about this as the protocol was designed to have zero-liquidations which benefits borrowers.
A portion of something. In this context, it means to split an asset into different levels of risk. Some tranches will represent a safe portion of the underlying asset, while other tranches will represent a riskier portion of the asset.
Senior claims are the most safe as they are paid back first. In return for this extra safety, they have limited upside -- usually only an interest rate on top of their original investment.
Junior claims are riskier than senior claims as they are paid back last. In return for this extra risk, they have a much higher upside. In the case of Button Tranche, they receive exclusive exposure to all of the collateral's upside.
An auction is a sales event where potential buyers and sellers place competitive bids and asks on assets in an open or closed format. There are many different types of Auctions (dutch, english, sealed-bid, etc).
Primary markets are markets in which financial market products are initially sold, typically to raise funds. An example of this would be sovereign bond auctions. Investors place bids and purchase U.S. Treasuries directly from the issuer (the U.S. government). For Buttonwood tranche tokens, this would be the ButtonAuctions market.
Following the issuance of products on the Primary Market, the Secondary Market is where assets and securities are traded amongst investors. U.S. Treasuries are commonly sold on the secondary market as investors adjust their portfolios to meet goals and risk parameters. For Buttonwood tranche tokens, this would be the ButtonZero market.