System Cleaner's Welcome screen is the first screen that you see when the application opens. You can also always return to this screen by pressing the button Welcome on the left System Cleaner panel.
Based on your use of System Cleaner features, namely Disk Cleaner and Registry Cleaner, the Welcome screen displays your System Summary to remind you when your system was checked last time and what the result was.
From the Welcome screen you can also activate the System Cleaner's Quick Maintenance tool which performs a quick all around maintenance of your system by automatically running Disk Cleaner and Registry Cleaner.