There isn't a single, definitive list displayed directly within the Excel interface that shows all available functions.
However, there are a few ways you can access this information:

1. Formula Help: When you start typing a formula in a cell and press the left parenthesis "(", Excel displays a dropdown list with suggested functions based on what you've typed. This can be a helpful starting point to explore relevant functions.

- Start typing your formula in a cell (e.g., =SUM().
- As you type the function name, a small box with function information will appear next to the cell. This box will show brief details about the function's purpose and arguments.
- Click on the function name within the information box. This will open a more detailed help window in the separate "Formula Editor" pane, providing a complete description, syntax (structure), and examples of how to use the function.

2. Insert Function: Click on the "Insert Function" button (often an f(x) symbol) located on the Formula tab.
This opens the "Insert Function" dialog box, which provides a searchable list of all available functions categorized by function type (e.g., Logical, Text, Math & Trig, etc.).
You can browse the categories, type part of a function name, or use the search bar to find the specific function you're looking for. Each function has a description and arguments (inputs) needed for the function to work.

3. Excel Help: The built-in Excel help documentation is a valuable resource.
You can access it by pressing F1 or clicking the question mark icon in the top right corner of the Excel window.
Search for "Excel functions" or browse the documentation related to formulas and functions.

4. Online Resources: There are many comprehensive online resources dedicated to Excel functions.
A quick web search for "list of excel functions" will provide you with detailed explanations, usage examples, and tutorials for all the available functions.

Microsoft itself provides a comprehensive reference guide for all Excel functions on their website: https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb

5. Third-Party Websites: Many third-party websites offer extensive lists and explanations of Excel functions, often categorized or searchable by function type.

Here are some popular choices:

Google Excel: https://googlexcel.com/
Kepler Works: https://keplerworks.com/

Exceljet: https://exceljet.net/functions
Ablebits: https://techcommunity.microsoft.com/t5/excel/excel-formula-returning-multiple-text-strings-in-a-cell/td-p/1445489

By using these methods, you can explore the vast library of functions available in Excel and find the ones that fit your specific needs.