Consider trying to open a jar. Perhaps its lid is screwed tight and you are struggling to open it. Friction is working against you, perhaps painfully so, as you might injure your hand in the process.
On the other hand, without friction, you would not be able to get a grip at all, failing to open the jar as well. Friction can get in the way, but is essential, too. It poses challenge, but also enables possibility.
You may reach for a towel to get a better grip, essentially affording yourself more friction (while protecting your hand) than what is holding the lid in place.
Friction here is largely something you see as a problem to solve. It is what is in your way to get the result you want.
In knowledge work, we often strive to remove friction as much as possible. Per my previous post, Software Sludge, this can be quite positive, when it is about the removal of unsightly sludge.
We use the term to mean this: any aspect of choice architecture consisting of friction that makes it harder for people to obtain an outcome that will make them better off (by their own lights).
Nudge, The Final Edition, by Richard H. Thaler and Cass R. Sunstein, page 153.
Removing friction is of course only half the story of effective friction management. Friction is also a valuable tool to deliberately make some things harder, for good or for bad: The same principle that helps a company make it more difficult for customers to cancel service also helps prevent people from actually making worse choices for themselves.
Typically though, the conversations seem to err on the side of friction removal, of making things easier. That seems especially so, when that conversation is in the context of productivity, often with the implied aim of wanting to increase speed of an activity or process.
Friction is an unavoidable fact of life and it can clearly have important uses, too. There are also times when it is less a problem to solve and more a struggle from which we gain.
Whether on the scale of evolution or a single lifetime, our minds are formed by friction with the physical world and the living beings with whom we share it.
A World Appears, by Michael Pollan, page 115.
That forming of minds is where friction plays a key role; it is part of how we learn. You have to engage in cognitive friction, in a productive struggle, where you wrestle with a problem, over time. This is how you grow intellectually, sharpen your thinking and deepen your understanding.
You benefit from the tedious work of learning a programming language and manually writing and editing a computer program, because it teaches you a way of thinking. Working through a math problem that is at the edge of your abilities is mentally difficult, but that cognitive work also improves your ability to do so, to reason with abstraction. Writing, carefully weighing the right angles, tone and wording improves your thinking. As you write, there is a good chance that you also learn.
In a service and information environment that tends to optimize for convenience, mental friction may cause some unease. More and more, AI usage tempts with the offer of quick answers and the easing of mental effort.
That mental friction then also becomes a useful signal. It serves as an invitation to engage with a struggle, rather than to hand off the thinking. There is value in that discomfort.
Friction encountered may not feel good. That does not mean it is not necessary, indeed some always is. Circumventing it or removing too much is then not actually a useful shortcut.
There are times when friction is not a problem in your way at all. It is your way.