Weekly gross pay is the amount on your paycheck each week before taxes and other expenses are taken out. Where as net pay is the final amount that is deposited into you account.
In travel healthcare there are many variables that determine individual differences in gross vs. net pay, such as taxes and health insurance. Some portions of your pay are not taxed, such as stipends and travel reimbursements. Other portions are heavily taxed, such as bonuses and overtime. The taxation rate varies based on the state you're working in, the amount of hours you work, your income level, your W2 status, and much more.