Many creatures can transform into other forms. For some, the ability is called "Shapechanger".

* Doppelganger: **Shapechanger**. The doppelganger can use its action to polymorph into a Small or Medium humanoid it has seen, or back into its true form.
* Jackalwere: **Shapechanger**. The jackalwere can use its action to polymorph into a specific Medium human or a jackal-humanoid hybrid, or back into its true form (that of a Small jackal).
* Succubus: **Shapechanger**. The fiend can use its action to polymorph into a Small or Medium humanoid, or back into its true form.

Meanwhile, other creatures have a very similar "Change Shape" ability:

* Deva: **Change Shape**. The deva magically polymorphs into a humanoid or beast that has a challenge rating equal to or less than its own, or
back into its true form.
* Night Hag: **Change Shape**. The hag magically polymorphs into a
Small or Medium female humanoid, or back into her true form.
* Oni: **Change Shape**. The oni magically polymorphs into a Small or Medium humanoid, into a Large giant, or back into its true form.

I'm not sure why there are two terms for abilities that appear nearly identical.

What are the mechanical differences (if any) between the "Shapechanger" and "Change Shape" abilities?