@abuzarkandwal
Expiration days - basic expiration days setup. I.e. membership expire after 30 days from purchase. User then can buy membership for 30, 90, 120 days. If I set expiration days to 10, membership will expired after 10 days from purchase. User can choose 10, 20, 30 days..
Item period - is related to item limits. There is setup what is maximum number of listings user can publish. If it is i.e. 10 items, then is question if 10 is total count, or it is just 10 per day, 10 per month or 10 per week? Usually this is not setup like user can publish 10 items at total and that's it, but limits are for certain period.