Confirms a formula as a legacy array formula, and Excel shows it in curly braces in the formula bar. In Google Sheets the same keys wrap the formula in ARRAYFORMULA.
Questions
Do I still need Ctrl+Shift+Enter?
Only in Excel 2019 and older, or to keep a workbook working in those versions. In Excel 365 and Excel 2021, press Enter and the result spills into the cells it needs.