Create, edit or delete records - They can create, edit or delete records in the CRM module to which they have access.
Edit associated records - A portal user can edit records that are associated with him, that are added by other CRM users, if they have the required permission. For example, if a deal or account is associated with the portal user then he can edit the details of those records.
Edit information in a record - They can edit the fields (even the ones present in subforms) on a record that is shared with them, for example address, phone number, email address etc. The changes will reflect in the CRM.
Clone records associated with the leads/contacts (deals, invoices, quotes, etc.) - They can clone other records that are associated with them and add more details as required. For example, if a portal user wants to replicate a deal, quote or invoice, then instead of creating a new record from scratch they can cone an existing record and make edits wherever necessary.