SPLIT(text, delimiter) cuts text at a delimiter and spills the pieces to the right: =SPLIT("Rivera, Ana", ", ") gives Rivera and Ana in two cells.
There's a catch in the third argument, split_by_each, which is TRUE when you leave it out. Then every character of the delimiter splits on its own: ", " splits at each comma and at each space, so "Van der Berg, Lotte" falls into four pieces. Set it to FALSE to split only at the whole delimiter: SPLIT(A8, ", ", FALSE). Pieces that look like numbers come back as numbers, so a code like 007 becomes 7.
Inside ARRAYFORMULA, SPLIT works on a whole column at once, one row of pieces per cell.
Going the other way, JOIN(delimiter, range) puts the values of one row or column into one text, empty cells included. TEXTJOIN(delimiter, ignore_empty, range) does the same, and with TRUE as the second argument it skips empty cells, so you don't get double commas.