An export often arrives with a different number of rows each week. A fixed range can miss the new records. A dynamic range uses a count or a spill reference to find its end.
OFFSET starts from an anchor, moves a number of rows and columns, and returns a range with the height and width you supply. It recalculates frequently in Excel, so use it carefully in large workbooks. INDEX can return the final cell of a range without that volatility. COUNTA counts text as well as numbers; COUNT counts numbers only. Neither approach treats a blank in the middle as the end of the list. When the data can contain gaps, use FILTER to choose populated rows explicitly.