SELECT 8 FROM TABLE_NAME execution process ?

I am using a sql query i.e.
SELECT * FROM TABLE_NAME
In this Table_Name table has 10 rows and 5 columns. When I run this above query it runs fine and return 10 rows and 5 columns.
Now I am running a new query i.e.
SELECT 8 FROM TABLE_NAME
Now it will return only a single column but 10 rows and this single column has same values i.e. 8 in each row.
I want to know that why it return me 10 rows and a column which has only 8 value and when i am using * instead of 8 in that case it will return 10 rows and 5 columns.
What exactly the difference between both queries and its execution process?