What are the differences between Connected and Unconnected lookup? - ETL

What are the differences between Connected and Unconnected lookup?

Connected Lookup:

- participates in mapping

- Returns multiple values

- Can be connected to another transformations and returns a value

Unconnected Lookup:

- It is used when lookup function is used instead of an expression transformation while mapping, where lookup does not available in the main flow

- Returns only one output port

- It cannot be connected to another transformation

- Unconnected Lookups are reusable.