I've been a member of eBay for awhile now, and I recently sold one item a couple of months ago. This was the only item I had ever sold. About a week ago, I receive an email saying that an automatic payment of $41 was withdrawn from my bank account. It said it was for eBay's Seller fee's, etc. I've only sold one item, so why am I being charged? I thought eBay was free? If I had know I would've been charged, I wouldn't have sold anything in the first place.

some items have listing fees and with all items ebay get's a percentage of the final sale price.

you had to agree to the terms before setting up an account and at $41 the item you sold must have been a substantial amount

Ebay isn't free. A invoice is a service charge. If you pay bills they give you invoices. It breaks down the fee's and is basically a extremely detailed receipt. Ebay and PayPal have separate fee's. Ebay is like 10% of the profit. While Paypal is like 10% of the profit and a fee of like $5 or something. I recommend using sites like Craigslist to sell things. It's generally speaking free.

Ebay charges for everything but sometimes they offer free insertion fees. You definitely must pay your Seller fee when you sell something and your Paypal fee when you get paid. That adds up to around 12% of your item cost+shipping cost. You should read how to sell. Ebay is a business. They exist to make money.

The invoice provides details about the amount due as well as any payments, refunds, discounts, credits, and fees that were applied to your account during the billing cycle.

"I thought eBay was free"

Why would you think that? I'm serious. Why would you think it was free?