It depends upon what you mean by 'in terms of the internet'.
If you're referring to the amount of free webspace offered to customers by an ISP, it's massive. (You could host several major commercial websites with that amount of space).
However, if you're referring to the monthly download limit which some ISP's offer, 500Mb is 'next to nothing'. (If you need to calculate your likely monthly download usage, use this calculator:
http://www.comparebroadbandpackages.co.uk/broa dbandusage.html
If you want to know how long a 500Mb download would take, it depends upon your connection. On a dial-up connection, it would take around 30 hours. With a 2Mbps broadband connection it might take around 45 minutes.
Chris