[General] Cant use / find apps

Hi

Since getting the S4, i have downloaded a few apps from the Play Store, but cannot find them on the phone itself. I went to the help section and followed the instructions and sure enough, it lists the apps and states they are 'installed'. Yet when i go into the apps section on the phone, they are nowhere to be seen. Also, after i have downloaded each one, a Play Store icon appears at the top, can someone tell me what that is??

Thanks

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