Form is a record that typically has just one person in its scope, this is the one sent to Sponsors from Sites. Each Site person working on the study in an investigator capacity completes one, so there are many per study.
Summary is a record (generally one per study) generated by the Sponsor and included in the regulatory submission for approval. It pulls/aggregates data from the individual Forms for all people across all sites who worked on the study. This record is not shared with Investigators.