When you open Excel, the default worksheet that appears is typically Sheet1. This is the first worksheet in your workbook, and it's where most people do their work. If you want to change the default worksheet that appears when you open Excel, there are a few different ways to do it.
One way to change the default worksheet is to go to File > Options > Advanced. In the 'General' section, there is an option for 'Default file location'. Here, you can browse to the location of your workbook (or any other workbook) and select it as the default. This will cause Excel to open that workbook whenever you launch the program.
Another way to change the default worksheet is to use a macro. A macro is a set of instructions that you can record and play back in Excel. To create a macro, go to View > Macros > Record Macro. From here, you can give your macro a name and choose where to store it. Once you've recorded your macro, you can play it back by going to View > Macros > Run Macro.
The last way to change the default worksheet is to use VBA (Visual Basic for Applications). VBA is a programming language that allows you to automate tasks in Excel (and other Office programs). To use VBA, you'll need to create a new module and insert some code. The code will tell Excel what workbook to open when the program starts.
To learn more about changing the default worksheet in Excel, check out this tutorial.