Either the day you applied for your loan or within three days afterward, you should have received from your lender a "good faith estimate" of the fees charged for closing. This good faith estimate includes fees charged not only by the lender, but all parties involved.
The uniform settlement sheet you receive at closing will be divided into categories so that it's easier to see what the charges are related to. For example, some of the categories are: payments connected with loan, the title, money that must be placed in escrow, money that must be paid in advance to the lender, the broker's commission, recording fees, and document preparation fees.
In your contract, you and the seller agree who will pay what and although it's likely you won't by paying all the closing costs, here's a general rundown on what some of those costs include:

The loan origination fee covers the lender's administrative costs. The loan discount, referred to as points (each point being equal to 1 percent of the loan amount), is extra interest paid to the lender to make up the difference between market interest and the interest of the loan.

Whenever governmental regulation, state usury laws and/or competitive practices prohibit the lender from charging a rate of interest which would make the real estate loan competitive with other fields of investments, the lender must seek some other method of increasing the yield for the investors. By charging "points", the lender can bring the real estate loan up to those other investments.

Yes. Commitment Fee, Discount Fee, Warehousing Fee, Funding Fee, etc.

FHA: The Buyer is usually charged with the Loan Origination Fee. The Discount Fee can be paid by the Buyer or Seller.

VA: The Buyer is usually charged with the Loan Origination Fee and the Funding Fee. Discount Fee may ; be paid by Seller, Buyer or split.

Conventional: Points can be paid by the Buyer, the Seller, or split between the two. State on Contract of Sale! City/County/State government sponsored loans: As published by them.