Unknown toolbar with plus signs below formula bar

Hi everybody. I recently got an excel spreadsheet to keep the record, with one unknown command - toolbar. Since I couldn't find answer anywhere I must ask if anybody knows the answer.

I attached a picture, print screen with that spreadsheet. Below the formula bar and above the column headings the one can see a "toolbar" with a plus signs. When the sign is pressed it expands and shows the hidden columns. When expanded sign changes to minus with a line over columns it refers to. Another click and it collapses. Works exactly like hide/show but is more handy since it is visualized, can make several independent and etc.

Spreadsheet is made in Excel 2003.

Although I can work without knowing what is it and how to make I am sooooo curious.

Thanks everybody in advance,
Cheers!