This build step exports various build job and hudson parameters into a property file named hudsonBuild.properties in the project workspace.
See Job Exporter Plugin Wiki for more informations.

build.jobName Name of running job.
build.id Build ID.
build.number Number of running job.
build.host Job runs on this host.
build.slave Job runs on this slave.
build.result Job result until this build step.
build.started Job started at this time.
build.elapsedTime Milliseconds the job is already running.
build.duration Human readable elapsed time.
build.executor
Executor number.
build.cvsBranch CVS branch, if configured.
build.svnRevision SVN revision, if configured.
build.gitBranch GIT branch, if configured.
build.user.id ID of user that triggered this job. Has value of "null" for anonymous user. Only filled if the build was trigged by an user.
build.user.name User that triggered this job. Only filled if the build was triggered by an user.
build.user.fullName Full name of user that triggered this job. Mostly identical with value of "build.user.name" (if ID is not null).
build.user.emailAddress Email address of user that triggered this job. If no user with email address was found, the admin email address stands here.
build.upstream.number Number of upstream job that triggered this job. Only filled if the build was triggered by an upstream project.
build.upstream.project Upstream project that triggered this job.
build.remote.host Remote host that triggered this job. Only filled if the build was triggered by a remote host.
build.remote.note Host note for remotely triggered job.
build.admin.emailAddress This is the current administrator email address.
build.summary Build summary like "Executor #3 for master : executing MyJob #28"
build.hudson.version Running Jenkins version.