what is difference between xd memory card type h&m ?

Answer 1

h is higher speed, it takes less time to put the data captured by camera on card because h has more data channels, or faster channels than m card
difference is only significant at very high shutter speeds or fast multiple exposures

Answer 2

Having worked in a camera shop, the only difference i know is that the high capacity cards are either M or H. There are only a few old Fuji cameras that do not support XD card type M or H.

Otherwise their only job is to write data into the card in the same way as any other storage medias.

Hope this helps.

Answer 3

speed