Most landlords on Uniplaces are people who rent a secondary property, but don't actually live there.
Other landlords, however, simply rent spare rooms in their main home, which means you will be living with them and, in some cases, their family members. In case they do, they are marked as a Resident Landlord. You can find that information in every listing.
There are also a lot of landlords who own several properties and/or manage several of them on behalf of other landlords. These properties are usually professionally managed, and may have specific rules (regarding deposits, payments, documentation required, etc).
As soon as you receive your booking confirmation email, you will receive more information about your new landlord.