SPY SPDR Unit Trust 1? What is it?

Hi just searching for a quick answer I thought this would be similar to the S&P500 but can be traded (spreadbetted) on IG. Wanted to know what it was or what's the difference?

Any information would be helpful.

Thanks in advance.

Vikash

Think I just found out what it is. It's an Exchange traded fund. Does this mean that on the stock market people trade the SPDR or SPY and can not trade the S&P500?

Just trying to get my head around these basics.

Vikash