what is the actual function of colspan coz changing the colspan number doesn't has any impact?

Answer 1

colspan makes the table column span. for example:
<table>
<tr>
<td>a</td><td>b</td><td>c</td>
</tr>
<tr>
<td colspan="2">d</td><td>e</td>
</tr>
</table>
will result in:
| a | b | c |
| d | e |
as you can see the column having the text "d" spans two columns.
just play around with the code in the Playground and you will get out it works.