Some small operational sheets put each person or asset in a separate column and list field names down the first column. That layout is convenient for a form, but it makes filtering and appending difficult. Transpose swaps the rows and columns. It doesn't summarize values or infer what they mean.
Inspect the raw layout before rotating it. If the file's first row contains record labels, keep that row in the data until after the transpose. Then promote the first transposed row to headers. Promoting too early can hide the labels you need.
The M function is Table.Transpose. You can use it in the Advanced Editor against the current Source table. After the rotation, rename the generic first column and declare the final types. A missing cell must remain in its original position, and a title row belongs outside the rotation.