What is an "acknowledgement" in the context of a naturalization application?

[xyzzy]

The "Naturalisation application processing timelines (only)" thread has people reporting a "Date of receipt of acknowledgement", typically the same day or soon after they applied. But what exactly is this acknowledgement?

I applied for naturalization (Tier 2 visa + ILR + more than 1 year) in mid-February 2024. The only things close to an acknowledgement I've gotten are:

* An email from no-reply@mail.ukvcas.co.uk with subject "Your supporting information has been submitted to UKVI". This says "We are delighted to confirm that the supporting information for your visa application for the following applicant(s) has been submitted to UKVI: <name>. All updates about your application will come from UKVI directly and NOT from UKVCAS." and is signed off as "UKVCAS Customer Services".

* An email from no-reply@mail.ukvcas.co.uk with subject "Your UKVCAS appointment - proof of attendance". This says "We are writing to confirm attendance at your UK Visa and Citizenship Application Services (UKVCAS) appointment." and has a PDF attachment. This is the proof of attendance that UKVCAS charges a small amount like £2 for.

Both of these were received soon after my biometrics appointment, on the same day. I haven't gotten anything else. Is there any other acknowledgement I should have received? What do people usually mean by acknowledgement on that thread?

[alterhase58]

That’s it.
The next communication is the approval email unless they’ll contact you for queries. They won’t give you any progress updates.
Don’t get nervous.. it could take up to 6 months, sometimes even longer (generally not a sign there's an issue with your application).