Jakarta (named after the place in Indonesia) was a grouping of Apache foundation projects in
Java. It helped organize things, since the Apache group is most famous for its http web server, which has no java in it at all.
Over the years, certain Jakarta projects became so big in their own right that they dropped the Jakarta name. But I think even to this day, you can find tomcat under the jakarta.apache.org/tomcat URL in addition to the tomcat.apache.org one.