This repeatable element is set to alternate its layout on every other repeatable added through the use of custom selectors. To see how this is controlled, with the Repeatable Container selected, click the dropdown on the right labeled "Whole Element."
There are two selectors, one for "every other repeatable image" and one for "every other repeatable text." Images are placed using absolute positioning so that they match the height of the copy. Text is simply floated left or right depending on whether they are odd or even.