OSM and OpenStreet Carto

I am new in OSM mapping.
Yesterday I edited online some buildings as OSM was not up to date (building deleted since the 80’ and not reported in official French land registry, but this is another story …).
Then I decided to use JOSM to improve my work.
When the tool was installed I downloaded data from OSM and found back my work of yesterday.
Then added imagery. I recognized Bing aerial as the imagery used when editing online.
Then I choosed “OpenStreetMap Carto (Standard)”.
The surprise is that in this imagery building I edited yesterday are correctly drawn. And better than what I was able to do yesterday using Bing imagery.
Up to what I know OpenStreetMap Carto is OpenStreetMap. So why is there a difference? Why is Carto up to date as OSM online not?

Thanks for all answers

Rendering (applying OSM data to the OSM tiles) can take some time. So edits you do today may appear on the tiles (in JOSM’s OpenStreetMap Carto and on the main website) tomorrow, or some time later. Are you sure you’re not simply seeing the brand new rendering your own yesterday’s edits?

Open your browser now. Is the building there? (Try a refresh, too).

edit: terminology fix

OpenStreetMap Carto is also called the standard rendering for OpenStreetMap. It is the map you see on e.g. www.openstreetmap.org
It is also the style you see when you download data in JOSM. As you can see on www.openstreetmap.org there are several other rederings of the same data. There are also “maps” based on OpenStreetMap data for mobile devices such as Garmin GPSes or smartphones.

So OpenStreetMap is the name of the project, and the project is collecting data to make maps.

Can you post a link to the area which you have edited, so we can see what is going on ?

He’s only made three changesets, all in the same area, and with not very useful changeset comments (“Improvements”). If this building is typical https://www.openstreetmap.org/way/501159414/history#map=18/45.90985/6.14628 he has been detailing external pillars, or similar, on the buildings.

This does just look like confusion due to delayed re-rendering, and possibly browser caching.