QVX (Qlik data eXchange) is a file/stream format for high performance data input into QlikView and Qlik Sense. A QVX formatted file contains metadata describing a table of data and the actual data in the table. In contrast to the QVD format, which is proprietary and optimized for minimum transformations inside QlikView and Qlik Sense, the QVX format is public and requires a few transformations when exporting data from traditional database formats.
Qlik custom connector is an interface developed by customers that enables data retrieval from a custom data source. Earlier versions of QlikView supported connectors implemented as dynamic-link libraries (DLL). Starting with QlikView 10, the preferred method is to implement Connectors as separate applications that reply to QlikView's and Qlik Sense‘s requests to connect to a data source and to retrieve data, as well as stream QVX formatted data to QlikView and Qlik Sense. Connectors are launched as separate processes when QlikView or Qlik Sense needs to retrieve data from custom data sources.