Conference papers refer to articles that are written with the goal of being accepted to a conference: typically an annual (or biannual) venue with a specific scope where you can present your results to the community, usually as an oral presentation, a poster presentation, or a tabled discussion. Conference papers are typically published in collections called "proceedings": sometimes these are printed by university presses, by professional organizations, by big-name publishers, or simply online.
Whereas, Journal papers refer to an article that's published in an issue of the journal. The frequency of issues for different journals varies from once-a-month to once-a-year, or anything in between; it may not even be regular.