Deals in any kind of market structure (fund, syndicated loan, etc) can contain multiple tranches. As explained before, the senior tranche will be filled by the pool as soon as the more junior tranches have been fully funded. Underwriters invest in the more junior tranches after having done due diligence on the deal and the borrower. In return for their investment, the underwriters receive tranche tokens. Tranche tokens are deal-tranche-specific, fungible, non-transferable tokens.