What is the exact difference between extrauser and useradd - yocto

Question

In one recipe i can see the following but it is not creating any extra user or group, that i confirmed while inspecting rpm file.
inherit extrausers
EXTRA_USERS_PARAMS = "\
useradd -p '' example; \
groupadd example; \
"
So I added the following in the recipe which created a user and group for me.
inherit useradd
USERADD_PACKAGES = "${PN}"
GROUPADD_PARAM_${PN} = "--system example"
USERADD_PARAM_${PN} = "--system -M -d /var/lib/example -s /bin/false -g example example"
What is the exact difference between useradd and extrausers in yocto. Why extrausers cannot able to create user and group.

Answer 1

extrausers add user/group at image level and cannot be tied to a specific recipe, and that's the role of useradd class, it can be used on a recipe.
Read the note here:
Note
The user and group operations added using the extrausers class are not
tied to a specific recipe outside of the recipe for the image. Thus,
the operations can be performed across the image as a whole. Use the
useradd class to add user and group configuration to a specific
recipe.
And here is the note for useradd:
The useradd* classes support the addition of users or groups for usage
by the package on the target. For example, if you have packages that
contain system services that should be run under their own user or
group, you can use these classes to enable creation of the user or
group.