When you are creating an assignment you can choose to have students submit different files and/or links.
File types include: PDF (.pdf), Zip (.zip), Word (.doc/.docx), Excel (.xlsx), Sketch App (.sketch), iPython Notebook (.ipynb).
Links: Any type of can be uploaded including GoogleDocs and Youtube.
Google Drive: Students can connect to their Google Drive and upload files directly from there.
Text: Students can type their assignment directly into the Peergrade text editor.
Video Recording: Students can record videos directly in Peergrade to submit.
Note: By default students can only submit one link or fill. To turn on multiple attachments go to Assignment Settings > Submissions.