Each module will only fit into a specific row when adding it in through the Experience Editor, the row size for each module can be found here in the modules section

A 12 column is known as page width

An 8 column is known as one column

A 6 column is known as one column reading width

Two 6 columns is known as two columns

Three 4 columns is known as three columns

An 8 and a 4 column is known as two columns wide left

A 4 and an 8 column is known as two columns wide right