Excel has recently introduced a huge feature called Dynamic arrays. And along with that, Excel also started to make a "substantial upgrade" to their formula language. One such upgrade is the addition of @ operator which is called Implicit Intersection Operator.

How is it used

1. The @ symbol is already used in table references to indicate implicit intersection. Consider the following formula in a table =[@Column1]. Here the @ indicates that the formula should use implicit intersection to retrieve the value on the same row from [Column1].

2. With the new Implicit Intersection Operator, you can use this to return a value from the same row in a Dynamic Range - for example: =@A1:A10

References

According to their documentation for Implicit Intersection Operator:

Excel's upgraded formula language is almost identical to the old language, except that it uses the @ operator to indicate where implicit intersection could occur, whereas the old language did this silently

Can you remove the @?

Often you can. It depends on what the part of the formula to the right of the @ returns:

• If it returns a single value (the most common case), there will be no change by removing the @.
• If it returns a range or array, removing the @ will cause it to spill to the neighboring cells.

If you remove an automatically added @ and later open the workbook in an older version of Excel, it will appear as a legacy array formula (wrapped with braces {}), this is done to ensure the older version will not trigger implicit intersection.

Like mentioned in the question, the use of @ symbol has been available in Excel tables from very long as part of Excel Table's Structural Referencing. But the "Implicit intersection operator" is pretty new and came along with Dynamic arrays.