Pipeline jobs allow building a continuous delivery pipeline with Jenkins by creating a script that defines the steps of your build. For those not familiar with Jenkins Pipeline, please refer to the Pipeline Tutorial or the Getting Started With Pipeline documentation.
The Jenkins Artifactory Plugin adds pipeline APIs to support Artifactory operations as part of the build. You have the added option of downloading dependencies, uploading artifacts, and publishing build-info to Artifactory from a Pipeline script, in addition to integration with build tools and package managers.
Scripted and Declarative syntaxes are two different approaches to defining your pipeline jobs in Jenkins. When working with the Jenkins Artifactory plugin, be sure to choose either scripted or declarative. In other words, do not use declarative and scripted steps within a single pipeline. This will not work.
More information on the difference between the two can be found in the Jenkins Pipeline Syntax documentation.