Depending on the company, part time jobs may or may not have guarenteed hours (in other words some weeks you'll be lucky to get one 8 hour shift while others you might get the full 24 (or 28) hours or anything in between.
Part time jobs usually also don't have guarenteed shifts; meaning one shift you might work evenings, another days, another afternoons and maybe even nights in some cases.
The length of the shifts is also variable, could be full 8 hour days but could also only be 4-5 hour days; so if you get 24 hours, it may not be three eight-hour shifts and could be four six-hour shifts or maybe even six four hour.
The shifts, hours worked etc vary wildey from company to company.
In some companies (espcially ones with high turnover) they'll start people on as part time staff as a sort of test to see if the job is right for them. If they 'last' for a certain amount of time, they'll probbaly be asked to go full time.
Guy# 1: What can say? It's a part time job; hours and shifts arn't guarenteed.