The Jupyter ecosystem got more complex in 2023. Want more background, see the second half of my answer here that references resources detailing how the Jupyter ecosystem changed a lot in 2023 with Jupyter Notebook 7+ now being built on the same components as JupyterLab.
The upshot of this is now it can be hard to tell what you are using for writing and running Jupyter notebook .ipynb files. However, knowing this can be important when you want to do something like display an interactive matplotlib-based plot or make a an animation.
KEY TIP: Older style has a 'Cell' menu along the File menubar.
Does the menubar the starts with 'File' include 'Cell'?
Example:
If it does, then you are most likey using the older tech style of Jupyter Notebook 6.4 or earlier or NbClassic (6.5 and forward).
Otherwise you are using modern JupyterLab or Jupyter Notebook 7+
Both of these will lack the 'Cell' menu being among the main menubar.
JupyterLab is more like an interactive development environment and so it seems more complex than the clean, document-centric interface of the Jupyter Notebook 7+. JupyterLab has icons on both sides of the main window you can use to toggle on abilities and panels. JupyterLab will let you click on the border of the windows and adjust the panes and arrange them.
The document-centric notebook interface for Jupyter Notebook 7+ is clean.
Has a varied interface considering what you are doing:
For example, there is a launcher pane:
Typical JupyterLab:
JupyterLab has view modes and can be highly customized in how panels are arranged. Be aware with only a quick glance, the single-dcoument mode of JupyterLab, toggled via the 'Simple' toggle in the button of the view above, may look like Jupyter Notebook 7+.
Single ocument mode with the file broswer toggled off:
Need to check the actual flavor of the interface and get specific version information?
Start with the UI:
See one of the 'About' menu entries under 'Help'.
Want more information?
Need specific version information in text or from the command line?
Execute in a running notebook where you are working the following code:
!jupyter --version
(Note that won't tell you though which interface you are using at the current time; if you have multiple Jupyter interface teach isntalled it will list them all.)
Combine that result with what you see from the 'About' and ouput results from %conda list or %pip list run in a cell in regards to the listings for nbclassic , notebook, etc..