In plain language
One-way is like a broadcast from the master copy; two-way lets people edit in either app and keeps both up to date.
Example
One-way: new CRM deals copy into a reporting sheet. Two-way: task status changes in either Asana or Jira update the other.
Related terms
Source of Truth · Data Mapping · Deduplication · Race Condition
Common misconception
Two-way sync is not just two one-way syncs; without loop prevention and conflict rules, each update can trigger the other endlessly.
Implementation guidance
Prefer one-way when possible, store each record’s ID from both systems, define which side wins a conflict, prevent update loops, and sync only changed records.