Transaction sources functionality in Projects suite

Hi Folks,

When we need to use transaction sources setup functionality?

Please specify the each check box functionality with suitable business example.

a) Raw cost GL Accounted

b) Import raw cost amounts

c) Import burdened amounts

d) Allow duplicate reference

e) Import employee organization

f) Allow Interface miscellanious

g) Purge After import

h) Process cross charge

i) Pre processing extension

j) Post processing extension

k) Processing set size