Here's the breakdown:
* 5: Indicates that the metal composition contains gold, with .5 indicating half of the composition or 50%
* 925: This usually indicates that the base metal is 92.5% silver.
Since jewelry marked "5925" also contains other alloys, the exact composition depends on the manufacturer.
In short, 5925 is most likely a mark indicating that the jewelry is made of 14K gold with .925 silver.