Excel offers a vast library of functions to perform various calculations, data analysis, and manipulation tasks. Here's a breakdown of some of the most common and versatile functions you'll encounter:

Basic Math and Statistics:

* SUM: This function adds the values in a range of cells. For example, `=SUM(A1:A10)` would add cells A1 through A10.
* AVERAGE: Calculates the average of a range of cells. For instance, `=AVERAGE(B2:B15)` would find the average of cells B2 to B15.
* MIN and MAX: Return the minimum and maximum values within a range, respectively. Example: `=MIN(C1:C20)` finds the smallest value in C1 to C20, and `=MAX(D3:D30)` finds the largest value in D3 to D30.
* COUNT: Counts the number of cells containing numbers within a range. `=COUNT(E4:E45)` would count the number cells with numbers in E4 to E45.

Text and Logic:

* CONCATENATE (or CONCAT): Combines text from multiple cells into a single string. `=CONCATENATE(F1, " ", G1)` would join the contents of F1 and G1 with a space in between.
* IF: This conditional function allows you to perform different actions based on a true or false statement. For example, `=IF(H2>100, "Over Limit", "OK")` would display "Over Limit" if the value in H2 is greater than 100, otherwise it displays "OK".
* VLOOKUP: A powerful function for searching data in a table based on a specific value. It allows you to retrieve data from a different column within the same table.
* HLOOKUP: Similar to VLOOKUP, but searches data in rows instead of columns.

Date and Time:

* TODAY: Returns the current date. `=TODAY()` would always display the current date when the formula is entered.
* NOW: Returns the current date and time. `=NOW()` provides both the date and time at the moment the formula is used.
* DATEDIF: Calculates the difference between two dates in years, months, or days. Useful for finding elapsed time or date calculations.

These are just a few examples, and Excel offers many more functions for specific needs. By understanding these fundamental functions, you can perform a wide range of calculations and data manipulation tasks in your spreadsheets.