In the Nonprofit Starter Pack, Households and Organizations can have multiple addresses. Their "primary" or "default" address (the one you would likely use for mailings) will be populated directly on the Account and Contact records. However, there is an "Addresses" related list on the Household or Organization Account that will list any additional addresses. Start and End Dates let you keep track of historical vs. current addresses, and there is also seasonal address functionality included in the package.
Each Household and Organization Account can have 1 default address. On that Address record, the "Default" checkbox will be checked, and that address will also display directly on the Account Record. When you update a Household Account's default address, it automatically copies to all of the Contacts in that Household.
What if one Contact in the Household has a different default address than other members of their Household?
NPSP allows you to "override" the Household address for a specific contact record
What if a constituent's address changes seasonally?
You can create Seasonal Addresses with a start month/day and end month/day and the nonprofit starter pack will automatically update the address on the Household/Contacts on the start day each year, and then change it back to the default address on the specified end month/day.
NPSP Documentation: Specify a Seasonal Address