You can search Subjects by clicking on the "Search Subjects" link on the lefthand side of the database -
Note that the Search defaults to the section you used last and is indicated in gray (here Subjects). If you are searching the default you can just click on Enter, otherwise first select the section (here either Database Items or the Marketplace).
The Subject Search will search the titles and also a field called "Also Known As" (or AKA). That allows users to find VW when they search for Volkswagen and vice versa.
When you see results you can further finetune those using the filters on the left-hand side -
As you set each filter a Filter Tag will be set on top of the left-hand side column -
Please note that Verified is set as default to Yes so that new users only get to see subjects that are complete and thus "presentable" (like on Wikipedia Subjects can be created on the fly when a user adds an item that has related subjects that hobbyDB had not covered prior).
Further note that you can use the Subject Likes similar to a bookmark as you can then later filter for them.
You can use the icons at the bottom of the Subject tiles -
Series is particularly useful if you want to browse a tree of products made by a specific Brand. Conversely, "Other Related Subjects" will show you all Subjects but Series.