"Update Miniconda" covers three separate maintenance jobs that people constantly run into each other: updating conda itself, updating the packages inside an environment, and refreshing a whole install by rerunning a newer installer over it. They use different commands and go wrong in different ways. Miniconda the installer, for what it's worth, has no update of its own; it's a snapshot of conda plus one Python, and once it has run, its job is over. Here are the three real updates, in the order you'll meet them.
Update conda in the base environment
Conda updates itself, and it happens in base because that's where conda lives:
conda update -n base conda
This is the exact form the official conda documentation gives today. Older guides, and years of Anaconda's own docs, tack a -c defaults onto the end, and the current docs dropped it for a reason worth understanding: the flag forces the update to come from Anaconda's defaults repository. On a stock Miniconda install that changes nothing, since defaults is already the configured channel. On an install you've pointed at conda-forge, though, it quietly drags base back toward the commercially licensed repo, and depending on your organization's size that has licensing consequences (more below).
Before touching anything, conda prints the plan of what it intends to change. Reading that plan instead of scrolling past it has saved me from more bad updates than any other habit I can name.
Why you update conda but rarely Miniconda
conda --version tells you what you're running, and if that number is current, the install is current, regardless of how old the installer that created it was. A Miniconda install from 2023 that has kept conda updated is functionally the same as one made from last month's installer, aside from the Python sitting in base, which project work shouldn't be using anyway (the guide on how to create and manage Miniconda environments makes that argument in full). New installer releases matter when you're setting up new machines. They ask nothing of existing installs.

