Popularism (Popolarismo) is a political doctrine conceived by Don Luigi Sturzo, which was the ideological basis for the Italian People's Party and later Christian Democracy. It can be considered as a synonim for Christian democracy.
"Popular" or "people's" in this context consists of two meanings. The first is the idea that the Christian-democratic parties should try to work towards a policy that is for the good of all the members of society, as opposed to parties that promote the good of a specific group (i.e. class). The second refers to a society where the people live in a kind of harmony, and where people and groups are interested in and care about each other. It isn't believed this goal can ever be attained, so it's more of a direction to work towards than a real utopian ideal.