There may be some other subtle difference but the big one is the free version is limited to 5 tags a month I believe, the paid version is unlimited. The free version used to be unlimited before they discovered they could make some cash off of it and came up with Encore. I bought the paid version when I first got my Evo, one thing though, the company that owns Shazaam is based overseas, the UK I think, and with Android there is no centralized system so Bank of America hit my credit card with a 13 cent 'international transaction fee'.