"Other" storage is content that your Mac does not know how categorize so it just bundles it up. Its primarily app support data and logs of activity, pretty much files that your apps need to run properly. But you can locate it. You open up finder and essentially start at the Macintosh HD and work your way down through the content, looking at the sizes and seeing where everything is being stored. You can see the sizes of each section by first changing the format of how folders are shown to a list view. Afterwards, select View from the menu bar and select Show View Options. This will pull up a window and at the bottom you should see "calculate all sizes", make sure it is selected and then select the Use as default button. If you are unable to still find where the storage is being taken up, it could be within the hidden library folder. If you hold down Option on your keyboard while clicking on Go in the menu bar, a Library option will appear there. I don't recommend deleting things in there unless you know exactly what it is because it could cause unpredictable behavior from your computer; that's why it's hidden. For a visual explanation, there are a lot of videos on YouTube if you search "calculate all sizes".