Slushminer is a cloud miner service, it means they provide mining service for you without you need to buy and maintenance hardware for mining. All you have to do is choose the package and invest money.
The problem with this service I think is more than 90% are scam, they didn’t pay you when due. This is happen to me 🙂
According to their schedule they have to transfer 0.005 bitcoin on 21 September but they did not. I already contact their support but no reply so far.
Stay away from this website, better to buy bitcoin gradually periodically.