Mail merge is a feature in Microsoft Word that allows you to create personalized documents, such as letters, envelopes, or labels, by combining a main document (containing generic content) with a data source (such as an Excel spreadsheet or a database) that contains specific information for individual recipients. This feature is commonly used for creating mass mailings or personalized communication materials.

Actually, in MS PowerPoint (and most other word processing applications), the key combination to move down one paragraph is "Enter". Pressing the "Enter" key moves the cursor to the next paragraph. If you want to move the cursor down one line within the same paragraph, you can use the "Down Arrow" key. There isn't a specific default key combination to move down one paragraph in PowerPoint; it's more about using the "Enter" key to start a new paragraph.

In Microsoft Excel, the default chart type for most data is the "Column Chart." When you create a new chart in Excel without specifying a specific type, it usually starts with a column chart where data points are represented as vertical bars. Of course, you can change the chart type later based on your preferences and the type of data you want to visualize.

In Microsoft Word 2019, you can add page numbers to your document by using the "Insert" tab. The "Insert" tab contains various options, including the "Page Number" option, which allows you to insert page numbers at different locations in your document.

In MS PowerPoint, the key combination to open the 'Save As' dialog box is F12. Pressing F12 opens the 'Save As' dialog box directly, allowing you to save the current presentation with a new name or in a different location.