If a user types in text that is longer than the cell's width, the text either carries into the next cell or appears truncated. If the adjacent cell to the right is blank, the text carries over; if the adjacent cell is populated, the text is truncated.
There are several ways to make the text not spill over into another cell, according to the Houston Chronicle. One option is to increase the width of the column by double-clicking on the top of the column that borders the right side of the cell. Another option is to merge the cell with cells to the right; highlight each cell, right-click and choose the Format Cells option, go to the Alignment tab and check Merge Cells. Alternatively, wrap the text by right-clicking on the cell; go to Format Cells, click the Alignment tab and check Wrap Text.