Somehow you navigated across the broad Atlantic to ebay.com (the primarily US site). Here most of the listings will be denominated in USD (US Dollars, displayed by ebay.com as "US $"), and those that aren't will have an "approximate"* conversion to USD under the actual price/bid in the currency of the listing or, on some pages, INSTEAD OF the actual price (this is the default setting on search results and in My eBay). Be aware that any bid/offer you make must be in the currency of the listing and when you pay the seller must be paid the full price in the currency of the listing (PayPal and other payment methods will convert your currency to the currency of the listing, but see below).
If you go back across the big water to ebay.co.uk you will likely find something similar but reversed: a higher percentage of listings in GBP (Great Britain Pounds, displayed by ebay.co.uk as "£") and some approximate* conversion display of those that aren't to GBP. Keep an eye on your address bar so you don't accidentally emigrate here again.
*Be aware the "approximate" in this case means ALWAYS too low: they are calculated using readily accessible "mid-market rate" quotes (an average of wholesale buy and sell rates of several large banks) while someone with funds in the approximately-converted-to currency (USD on ebay.com, GBP on ebay.co.uk) will have to pay someone their retail "buy rate" to pay the seller the correct price in the currency of listing; if PayPal does the conversion (and the new checkout popups on ebay.com seem to have done away with the ability to have PayPal bill your credit card in the currency of the listing, thus paying your credit card's possibly lower buy rate) its buy rate is 3% above mid-market at the time of payment (I think it calculates them once a day).
