This dialog box randomly displays to you one of the tips explaining some feature of ReSharper. If you like to view more tips, click Next Tip or Previous Tip. By default, ReSharper Tips appear each time you start Visual Studio. If you do not want ReSharper to display tips on startup, click I know it all!. Also, you can turn ReSharper tips on and off with the corresponding check box in the Environment | General page of ReSharper options.
You can aways view some random tip by choosing ReSharper | Help | Show Tips in the menu.