Command + H (Mac) | Control + H (Win), toggles the visibility of several features including layer and selection edges, paths, guides, grids and more. To control exactly what is toggled on/off choose View > Show > Show Extra Options. Here you can choose exactly what you want to hide and show.
Note, the first time you use this shortcut on the Mac OS, Photoshop will display a dialog asking “Would you like to use Command + H to hide Photoshop (Mac standard), or to hide/show selections, guides, etc. (Photoshop traditional)? Click “Hide Extras” unless you want to “Hide Photoshop” every time you use the shortcut. If you do choose to “Hide Photoshop”, you can change this behavior later by choosing Edit >Keyboard Shortcuts. Set the “Shortcuts For” to Application Menus and toggle the disclosure triangle for the View menu. Scroll down to Extras, change the Shortcut back to Command + H and click Accept and then OK.