What is managed dependencies in maven repository website?

The dependency you are looking at is not a jar file but a pom.xml that is meant to be used as "bom" (bill of materials). It contains the preferred versions of dependencies, so you would not need to inherit from that parent pom to use those version numbers but you can import them. See BOM section in the introduction: https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html#bill-of-materials-bom-poms

if you look into that pom.xml file: https://search.maven.org/artifact/org.apache.logging.log4j/log4j/2.13.3/pom you will see the dependencyManagegement section. If you import that pom that section is added to your own dependencyManagement secion (sort of). Its not dependencies yet, just preferred versions.

these kind of dependencies can only be added into the dependencyManagement section of the pom.xml - I assume the gradle dependency resolution follows that behaviour but I'm not sure about that, bom support took a while in gradle to be supported.