I have bought a lot of things on eBbay and used to work at the store that store stuff on
eBay.
eBay can be amazing but you have to be your own advocate and buy smart.
Amazon is a retailer that sells things. They are an online store. There is an
amazon marketplace also but it is decently regulated.
eBay is not a retailer or a store - it is a source for people to sell their stuff. So, you can be buying from anyone. Some businesses sell on
eBay but it is a lot of just regular people. Go into it thinking of it more as a fancier less hippie craigslist than an
amazon.
If you are going to buy from
eBay I would only use a credit card and do all of your payments through PayPal. If you do not have PayPal account then get one before you start. Both PayPal and your credit card can protect you if you do run into a case of fraud. (I have only had one problem in 10 years but it was on something pretty expensive so I was glad I have protected myself.)
I would not buy anything from anyone that doesn't have or won't send pictures. Look at a persons's feedback before bidding. Make sure that you read EVERYTHING in the auction. Pay attention to shipping prices and rules and keep in mind that it is an international marketplace. I try to only buy into the US unless I really want to deal with international. (Keep in mind that international is going to be more of a risk)
If you have questions send them a message and ask. If they don't respond then don't bother. Be a good buyer and pay in a timely manor and give feedback. Also keep in mind that they will be giving you feedback also and sellers can choose not to sell to people with bad feedback. It always pays to be polite.