Credit is the amount of money that a company will lend to you, and debt is the amount of credit that you have borrowed and still owe.
Your credit score has many components: payment history, amount of available credit that you are using, length of your credit history, types of accounts (credit mix), and new credit.
A loan is a type of credit, and assets are things of value that you own by yourself without owing money on them.
Collateral is assets that you can use to secure a loan, so that if you don't pay what you owe the lender can take those assets from you to recover the amount you owe them.
Installment credit is a loan that you pay in chunks every month/year. Revolving credit is automatically renewed as you pay off the debt. If the credit amount is $1000, and you borrow $500 you will have $500 left. If you then pay off $200 you will automatically have $800 of credit available to you.