Amazon is running an Amazon Prime promotion  where they will give you a one month free trial of Amazon Prime and a $10 credit towards products sold by Amazon.com. This offer is for new Amazon Prime members only and expires July 28th.
Amazon Prime  is their fast shipping program that offers free two-day shipping on any order and $3.99 expedited next-day shipping. The program normally costs $79 a year.
It’s likely that signing up will have you automatically renewing. To change that setting, read these instructions from the last Amazon Prime promotion .