What are the three grades of silver soldering?

The three grades (when used in jewellery making) are: 'Easy', 'Medium' and 'Hard'.

These refer to the temperature that the solder melts - 'Hard' is the highest, 'Easy' is the lowest.

The different grades allow a joint to be soldered, next to an existing joint. Thus you would normally use 'hard' first, then 'medium', and finally 'easy'.