The short answer is yes!
If you have a CSV of your people, you can import that CSV into Planning Center People. Once imported, all of your applications (Giving, Registrations, Check-Ins, etc) will be able to access those people.
If you have custom data for your people in that CSV, you might need to add custom fields to Planning Center People so there's a place to put all the data you are trying to import. Be sure to take a look at the CSV you're importing and ensure that there's a place in Planning Center People for all that data before importing the CSV.
Household (Family) Data
Though the CSV importer can generally only import data with 1 value for each person, it can also import households, where there are multiple people in each household. You'll need to define a Household column in your CSV (named anything you want), and each person in the same household should have the same value in that column.
For example, everyone with "Smith Household" in that column will be placed in a Household together. Everyone with "1" will be also be placed together. It doesn't matter what the actual household value is, as long as they match, they'll be placed in the same household. The Household will automatically be named based off of the last name of the first person added to the Household.
Giving (Donation) Data
Currently, there is no way to import giving data (donation history) into Planning Center. Giving is one of the younger applications in our suite, but we hope to add an import feature in time as it's a highly requested feature.