Often in Excel, you'll want columns or rows to continue to appear when you scroll off to the right or down the page.
You may have a table of employees with names down the left-hand side, with data pertaining the individuals disappearing off the right-hand side of the screen. Scrolling to the right, you'll want the names to continue to show when you hunt across for their NI numbers, stock plans, start dates.
And when you scroll down the page to get to the individual you're interested in, you'll want the column titles to continue to appear, so that you know which column you're looking in.
There are two ways to do this: the right way and the wrong way.
First: the wrong way. A feature has existed in Excel since I can remember called Split. It used to be on the Window menu, and now sits on the View ribbon. As its name suggests, it splits the window. You can either split the screen into two sections (a top and a bottom; or a left and a right); or you can split it into four.
The trouble with this method is that all of the panes are still navigable. So you can scroll up or down, left or right in any of the two or four panes that appear.
Just try it. Try splitting the screen and then do some scrolling in each of the resulting panes. Confused? You betcha.
Another minor annoyance with this technique is that the bars that separate the panes are distressingly ugly.
The Split function does have its uses—it can be useful to show multiple areas of data at the same time, to allow data entry that relies on other data in the worksheet. But more often than not, it's not the right tool.
Now: the right way.
The right way is through Freeze Panes. It can be found right next to the Split function. The main difference between this and the Split function is that with Freeze Panes, you can only navigate in the bottom-right pane. The top section remains frozen, as does the left section. This reduced functionality is a blessing. Trust me on this.
Oh, and the dividers are much more pleasing to the eye.
With either method, you invoke the dividers by navigating to the cell immediately below and immediately to the right of where you want them to appear. With Split, you also have the option of dragging a little divider immediately above the vertical scroll bar, and a similar one immediately to the right of the horizontal one.