By default, Excel uses the A1 reference style, which refers to columns as letters (A through IV, for a total of 256 columns), and refers to rows as numbers (1 through 65,536).
These letters and numbers are called row and column headings.
Excel can also use the R1C1 reference style (that need to enable manually), in which both the rows and the columns on the worksheet are numbered. The R1C1 reference style is useful if you want to compute row and column positions in macros. In the R1C1 style, Excel indicates the location of a cell with an “R” followed by a row number and a “C” followed by a column number.
If you don’t know how columns and rows are labeled numerically in Excel spreadsheet. Don’t take stress. Seems like by accidentally or by someone else enabled R1C1 reference style.
Don’t need R1C1 reference style and want to revert to A1, the default one, read the below article.