This Photoshop search panel has changed over time, so some features that were quite useful are no longer available and others have replaced them. You can discover tutorials, commands, photos, previously opened files, latest updates to the application, fonts, quick actions, stock, plugins, community etc and the range of features depends on the version you are using (in this document, it will be the latest version). It is a powerful core feature for beginners as well as advanced to find all kind of information and images, projects etc related to your work.
Go to the edit menu and click search and the panel will be displayed.
You have an edit field at the top of the panel and you can type in layers, smart objects etc - anything associated with the application and it will give you suggestions on how to use that such as tutorials, hands on tutorials on the subject as well as the basic command's location (or tools) and also it will often apply that effect or at least display the panel or dialog etc.
You can also check out tutorials related to that item where it will give a large amount of ideas, details etc. Also you have hands on tutorials where you have a step by step guide to the subject as well so if it is layers then you will see how to use them, manipulate them, use them as this or that etc.
You can also find out more via the handy links at the bottom of the panel such as links to the Adobe's help as well as fonts associated with that name as well as plugins associated with that subject and also it will send you to the community section where you can find the answers and ask more questions about that subject with fellow users of your favourite application.
You also have a section of what is new, which is useful as it gives all the latest update details, enhancements, things removed or changed etc. I have to say I am always checking out the what's new feature especially for things such as the recent update to webp format file support which has proved very useful for creating webp images for my site.
You also have access to quick actions which is a list of 15 (maybe more or less) actions that you can click and run such as select the sky or turn background blurred etc. Must admit, I wish they had not called them quick actions as it confuses with the existing actions but these are actually quite useful and produce some interesting effects or make certain tasks a whole lot easier. Of course with any quick action, the results can be variable.
You can also send feedback to Adobe. This is super useful as if there are things you have found that are in error in the application or there are features you would like to see if you would like to see enhancements to existing features then it really is a good thing to let Adobe know as then hopefully if they receive enough feedback then things will be changed and you will see that new improved shapes feature or better brushes etc or a fix to an issue that has bugged you for ages and ages.
At any point you can always return to the home page by clicking the home button or the back arrow. In earlier versions, you could also search for files previously opened but sadly that feature seems to no longer exist which is a pity.