Combo takes individual items and packages them together for a discount.
Add a Combo item is an option that was introduced with Orders2me version 2 and it can only be used if you have updated your menu to version 2. Otherwise you wont see the Add Combo Button.
Combo can be added by going to your menu from your restaurant's dashboard, clicking the category in which you want to add the combo and then click the Add Combo button.
This will open a new page where it gives you the option of adding individual items to create a combo.
This is the same process as adding an individual item, in the Basic Information section, you have the option of setting the name and the description for that combo.
In the Included Items / Combo Steps section, you have the options for adding individual items with different settings on them:
Name: this will appear on the page of the selection of items, during the ordering of combo by the customer
Description: a description of that item
Item Quantity: quantity of that item on combo
Override Total Price: override the original price.