Append stacks rows from compatible tables. Power Query aligns the rows by column name, not by the physical position of the columns. A western depot can put Receiver first while the eastern depot puts Unit first; the append still maps their matching headers correctly.
A new or missing field changes the combined schema. If one table lacks Receiver, its rows receive null in that column. If another table adds Note, the combined table gains Note and other rows receive null there. This is useful evidence about the source, not an instruction to invent a value.
Different names describe different columns until you normalize them. Cases and Count don't become one measure simply because their values look alike. Rename equivalent fields before appending. Then choose the columns required by the downstream contract. Keep deliberate zero values, and leave absent descriptive fields null unless the receiving team has approved another meaning.