Have you ever taken a shot and while you're sure you nailed the focus, it's a little bit softer than you'd expected? Perhaps your lens needs calibrating to ensure the autofocus is perfect.
It's worth noting straight away that lens autofocus calibration is only generally needed for DSLR shooters. Mirrorless cameras tend not to lean on the lenses to secure a perfect focus and the sensor will do the heavy lifting, correcting any imperfections. However, with DSLR cameras, the lenses can vary on sharpness in part due to calibration. Typically this will happen over time through general wear and tear, and a tool is needed to get it pin sharp again. In this video by Karl Taylor, however, he shows a way of returning the lenses back to their former glory without having to go out to buy anything.
I first noticed this problem with one of my oldest lenses which I was using for macro. I felt as if I was missing focus ever so slightly, far more often than I used to. I put it down to user error for a while before realizing that the lens might be slightly out of whack, and it was. Using a similar DIY technique, I applied a pretty heavy in-camera adjustment to compensate for the defect and immediately felt the impact. With a lot of photography, it's barely noticeable, but when you're doing commercial photography, macro, beauty, or anything where detail is paramount, your work's quality will be slightly inhibited and that will continue to grow if left unfixed.