Terminal designations
The purpose of the terminal-designation system for automotive electrical systems specified by the standard (DIN 72552) is to enable the most accurate connection of wires to all the various devices, above all when making repairs and installing spare parts. The terminal designations (Table 7) do not identify the wires because devices with different terminal designations can be connected at the two ends of each wire For this reason, they need not be written on the wires.
In addition to the terminal designations listed, designations according to DIN VDE standards may also be used on electrical machines. Multiple connectors, for which the number of terminal designations as per DIN 72552 no longer suffice, are numbered by consecutive numbers or letters whose function assignment is not specified by standards
http://www.bosch-classic.com/media/e...eichnungen.pdf

automotive relay guide - Relay configurations and types https://www.12voltplanet.co.uk/relay-guide.html