You may create a table with wiki notation:
||column 1||column 2||column 3||
|cell value 1|cell value 2|cell value 3|
If you would like to get a more sophisticated table, you may want to have a look at the Table Grid Editor plugin, which lets you create a table as a custom field.
I went through your first response and tried using a behaviour. I was successfully able to display text in Description field using a behaviour. But, I need to know the function to be used to populate a table in the description field. I have googled and all that I see is to how to CREATE TABLE in a database but I don't need that. All I need is to create a simple table with rows and columns having column headers so that users can input their details into the table.
I've also checked the Table Grid Editor plugin but I need this for the system field (Description) but not for custom fields in my case.