If you freeze the pane, you can scroll right or down and keep the row/column
headers visible so you know what you're looking at.  To demonstrate, enter
the months Jan...Dec in A2:A13 and the days of the month, 1...31 in B1:AF31.  
Now suppose I ask you to enter the number 5 on November 28th.  It's hard to
tell what cell that is;  as you scroll to the column labeled 28, the month
labels scroll off the visible window.
Now go back to cell B2.  Select it, then Window > Freeze Panes.  Now go to
November 28th;  it's easy because the headers are frozen.
FYI, the printout equivalent to freezing panes is available under File >
Page Setup, on the Sheet tab you select 'Rows to Repeat at Top' or 'Columns
to Repeat at Left'.

homework?