My radio-club recently got a Yaesu FT-225RD transceiver and I'm trying to digest its manual (available for download here). This is the first ham radio that I'm learning how to use, so I could be missing something obvious.
On the front panel there's a knob marked CLARIFIER and the manual has following description for it:
The clarifier control allows a means of offsetting the transceive or receive frequency by ±4 kHz from the frequency established by the main VFO dial.
I do understand that radio's frequency will drift with time and that not everyone's rig will be spot on channel and that in such cases minor adjustments may be needed to improve reception.
What I don't understand is when would use of clarifier be preferable to use of the main frequency dial. From what I can see, the main dial offers pretty good resolution for frequency adjustment and clarifier isn't a fancy name for a fine-tune knob I've seen on on radio receivers for commercial FM band from the same time period.
UPDATE: One thing that I didn't find relevant to the question at first is that in addition to the clarifier knob, there is a clarifier switch as well which is used to set clarifier to one of 3 settings: transceive, receive and off. This would imply (at least in my opinion) that in transceive setting, the clarifier would affect frequencies of both transmission and reception.