/usr/share/zsh/help/bg is in zsh-common 5.4.2-3ubuntu3.1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 | bg [ job ... ]
job ... &
Put each specified job in the background, or the current job if
none is specified.
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