Financing means asking any financial institution (bank, credit, union, finance company) or another person to lend you money that you promise to repay at some point in the future.
For instance, if you want to buy a vehicle but not having enough cash in your hand.
The dealer will look for a bank that will finance it for you. Upon approval, the bank will pay any product dealer the money for the product, and then they will send you a bill each month. The bank will lend you this money if you agree to pay interest on top of the money lent to you. In other words, financing is borrowing money with a promise to repay that money and some additional fees or interest, over a period of time.