If you are new to ebay, be sure to always send your items with a tracking number. If you do not have a tracking number, you cannot prove that the buyer received the item.
If you use the USPS website for shipping, the priority mail comes with automatic tracking numbers. You can find the tracking numbers in your mail history.
If you are shipping first class with the US Post office, you will not get a tracking number, so it is best, in situations where you are mailing items and want to only pay for 1st class shipping, to buy and print your shipping right from your My Ebay page. They will give you a tracking number.
WesleyGW of YouTube goes into great detail about how these buyers (and there aren’t that many of them, really) operate. If you are new to Ebay selling, you might want to check it out.
WesleyGW has a great YouTube channel for anyone who is new to Ebay or even thinking about Ebay. Check her out.