colspan is an attribute used inside table element with TD tags. it is generally used when a value is common in any no. of consecutive columns in the same row.
For e.g. <tr><Td colspan="2">DATA HERE</TD></tr>
here the value of colspan is 2. That means the cell of the table in which it has been given will take the space of 2 columns. Or simply it will skip the cell of the next column in the corresponding row. on the other hand it will be common in the 2 columns.
NOTE - 2 specified here is the no. of COLUMNS which is variable.