I have this excel form that gathers data from an external source and
references other columns in other sheets. I do not understand what this is
trying to accomplish

=IF(ROWS($1:1)<=COUNTIF(J$2:J$645,'Budget
Input'!B$5),INDEX(K$2:K$645,SMALL(IF(J$2:J$645='Bu dget
Input'!B$5,ROW(K$2:K$645)-ROW(K$2)+1),ROWS($1:1))),"")


I think it says for a row (with $1 being variable) Count the column J and
index them against column K, if a value in J equals Budget Input worksheet
cell B5, then match the existing rows in K - ...here is where I am lost...