Hi Arghya,
1. Assignment of storage unit type to storage type -
Based on the physical characteristic of the storage type & SUT you decide what are the storage unit type which can fit into this ( in a simple term Storage unit type is a storage media in which you store material this can be a pallet , basket, carton ) if you are having an area of Length X Breadth X Height of 5 x 2 x 5 mtr then you can accommodate 4 pallet ( 4 x 1.2 mtr) which are having a size of 1.2 mtr x 1.2 whereas in the same rack if you want to store basket which are probably 1 mtr of LBH then you can store more then 4 so the decision of assignment of storage unit type to storage type is based on the physical characteristic of Storage type and Storage unit type
2) Assignment of storage unit type to storage bin type
Similarly to above example you will always have an area where you can store only basket or only pallet hence it is very important to give a identification to that bin so that only that only the SUT which are meant for that area can go during putaway
Let me know if you need further input