As per my knowledge, both words are same.

Level span is used to eliminate duplicates in data, in Cognos it is used
repeat grouped item. Using level span we can see the grouped data group by
group.

For example, when country and city are both grouped, you can choose to show the
country name each time .

-- the country changes, by spanning Country by Country

-- the city changes, by spanning Country by City

-- there is a new record, by specifying no spanning

Spanning one grouped column by another column is helpful if the second

column contains many items.

Steps

Open the report that you want.

Click the column for which you want to set the group span.

In the Properties pane, click the Group Span property and click the

column you want to span.

Thanks,

Siva