what does din 975 mean?

DIN975 is a German standard threaded rod.

other fastener standard :

DIN German standard, GB national standard, ASME/IFI/ANSI American standard, Q auto standard, PEM standard, JB standard mechanical department, EN European standard, ISO international standard, JIS Japanese standard, HG chemical standard, NFE method Standard, UNI Italian standard, BS British standard, other commonly used standards.