Can someone tell me the difference between silver solder
alloys making with Ag 1000, Ag 950, Ag 925?
The numbers; 1000, 950 & 925 are the parts per 1000 of fine silver
in the alloy. The alloy marked 1000 is pure silver, also called fine
silver. The ones marked 950 & 925 contain 950 & 925 parts fine
silver per unit of measure (oz, gram, lb, kilo, etc.).
The 925 alloy is typically called sterling silver. Usually the other
metal used with sterling is copper, but that is changing with the
addition of other metals that give silver alloys with different
characteristics that can still be called sterling.
Based on this question & several others, I'd suggest you check with
a local library for books on jewelry making & metal smithing. If you
were in the US, I'd suggest a copy of the book, The Complete
Metalsmith. It has lots of good info, figures & diagrams for the new
& experienced metalsmith.