"Investment banks" create loan agreements that cater to the needs of the investors whose funds they attempt to attract; "investors" are always sophisticated and accredited organizations not subject to bank regulatory supervision and the need to cater to the public trust. Investment banking activities are supervised by the SEC and their main focus is on whether the correct or proper disclosures are made to the parties who provide the funds.
In certain cases where you have repaid some installments of a previous student loan independently, you would be given the authority of branching away the Co-borrower. This is known as Co-Borrower Release and by doing so, you ensure that the loan repayment is entirely yours. This also puts you in a position where you are not hit by the Credit History of your Co-Borrower. Both of you are separate entities speaking from the loan perspective and you would hence need to take charge of repaying your loan off.
For commercial banks and large finance companies, "loan agreements" are usually not categorized although "loan portfolios" are often broadly characterized into "personal" and "commercial" loans while the "commercial" category is then subdivided into "industrial" and "commercial real estate" loans. "Industrial" loans are those that depend on the cashflow and creditworthiness of the company and the widgets or service that it sells. "Commercial real estate" loans are those that repay loans but that depend on the rental revenues paid by tenants who lease space, usually for extended times. More granular categorizations of loan portfolios exist but these are always variations around the larger themes.
The final fourth sections contains standard text including details such as contract information, the relationships that exist between the finance parties - in the event of more than one tender and more than one law that apply to the agreement.