[doodpants]

The traditional interaction model of the Mac is that you select a file, and then choose a menu command to operate on it. Cmd-O is the keyboard shortcut for "Open".

Note that you can also use Cmd-down_arrow, because Cmd-up_arrow and Cmd-down_arrow can be used to navigate up and down the folder hierarchy, and the latter also works if you have a file selected rather than a folder.

Edit: Cmd-Delete will delete a file. I think the philosophy is that Cmd is used for commands, and Delete by itself is meant for text editing. One thing I like is that Cmd-Shift-Delete will empty the trash. I'm unaware of a keyboard shortcut for emptying the Recycle Bin on Windows, or any way to avoid the confirmation dialog when doing so.

[fireattack]

>the latter also works if you have a file selected rather than a folder

Wait, how do you "navigate down the folder hierarchy" if you don't select a folder? There is no deeper hierarchy.

[PascLeRasc]

If we Mac users want to go through a bunch of files in a directory quickly, we usually press spacebar in Finder on the first file and use up/down arrow keys to navigate. Spotlight will open up each file in a read-only view and will handle basically anything - STLs can be viewed and rotated, CSVs will show in a spreadsheet format even if you don't have Excel or Numbers installed, MP3s will open in a mini player, C header files will appear with colored formatting. It's so handy.

[fireattack]

Yeah I have seen the preview function, it definitely is pretty handy!

[doodpants]

You do select a folder. I'm saying that Cmd-down means "go down into this selected folder", but it also works if the selected item is a file.

BTW, I didn't even know about Cmd-Enter until aidos mentioned it; so that makes 3 different shortcuts to open a file. Convenient! :-)

[fireattack]

Ah, I understand now.

Windows is similar but with alt: Alt+up=up, Enter=down (or open). And there are also alt+left and alt+right as back and forward.