Unfortunately that fits the scam scenario to a 'T'. They are offering you $100 to shop Walmart and perhaps another store like Home Depot. They promise that you will be earning $400 per week or some such in the future. You respond to the preliminary email and they have a "live one". You then will receive a check usually of around $3000 to $4000, usually in an odd amount, such as $4593.78. It then becomes the classic pigeon drop. You need to deposit the check in your bank account, do your shops and the final shop is "Western Union" where you will be wire transferring on the bulk of the money. What you bought at Walmart or Home Depot is indeed 'yours to keep' because the check they send you bounces and the bank backs out the entire deposit from your account plus, often, check bouncing fees and you are obligated to pay the bank back.
The checks look good, they are drawn on a legitimate company except that they are forgeries. The bank can call ahead and verify the account and that there is a balance to cover the check, but the legitimate company on which the checks are drawn dishonors them as forgeries. It may take as long as 2-3 weeks before the check is bounced back to you, so don't assume that it being 'cleared funds' after 7-10 days has you out of the woods on it.