What Markdown is
A Markdown table is rows of pipe-separated cells with a dashed rule under the header. Alignment is set by placing colons in that rule.
README files, GitHub issues, documentation sites, Obsidian and Notion.
What Excel is
An Excel workbook is a zip archive of XML parts describing sheets, cells, formulas, styles and charts. The .xlsx extension is that format; .xls is the older binary one from before 2007.
Finance, operations and anyone who received a file from finance or operations.
What changes when you convert Markdown to Excel
Leading and trailing pipes are optional and both are handled. A pipe the author escaped with a backslash is read as data rather than a column break, which is the usual reason a hand-written table parses one column too wide.
You get a single sheet with a header row and column widths sized to the content. Values are written as text unless type inference is on, which keeps identifiers like 0044 or 007 intact.
What carries over from Markdown to Excel
One property of the Markdown has no home in Excel, and it is worth knowing which before you convert.
Excel wants a type for each column, and Markdown does not record one, so each column is typed from what its values look like. A column of digits that should stay text - a zip code, a phone number, a leading-zero id - is the usual thing to check afterwards.
Excel has no separate idea of a header, so the column names become an ordinary first row and nothing in the file marks them as different from the data.