Many times, when you are trying to copy text from one system to another you want to concatenate multiple elements but you also want to format it onto multiple lines. A good example is address lines - in Xero, the address lines are split into address line 1, address line 2, address line 3 but in Salesforce there is just one field called billing street. Here's how you do it:
Simply add a "\n" when in formula mode between quotes to signal that you want a new line between two parts of the string.
Of course, this can also be done with text mode by simply pressing Enter/return. However, using formula mode allows you to manipulate the individual pills within the field, allowing you to make powerful modifications to your fields.