Originally posted by Tele Master
What is conditiong the fretboard? Is it another way of saying "cleaning it"?

As pstring says, these are products that clean and partially seal the surface of the fretboard to prevent rapid loss or absorption of moisture. Lemon oil is probably the most widely used, because it works well. Rosewood has a fairly 'open' grain to it, which creates a lot of pockets to trap dirt, and a lot of surface area to exchange moisture with the ambient air. Both ebony and maple have a closer grain structure which requires less attention to sealing, but still needs to be kept clean.