Are you talking about the screen that pops up when some applications crash? Sometimes it asks if you want to send the info to Apple? Is that the one you're talking about?
I don't have one in front of me to work with but if that's what you're talking about, you should be able to highlight all the text within the screen with your mouse pointer while holding down the left-mouse button (assuming your left mouse button is active), continue to drag the mouse pointer downward highlighting all the text.
Now right-click the mouse button and choose copy (or command-c on the keyboard). This will copy the text into a buffer. You can now input all that text into an email or other application screen by pasting it by pressing your right mouse button and choose paste (or command-v on the keyboard).
If this is not what you're talking about Mac OS X (like other UNIX) have something called syslog and there are also crash logs located in ~/Library/Logs/DiagnosticReports/ Within this directory you'll find other sub-directories for various application crash logs.
You can also go to the folders for Applications > Utilities then open the Console. Various system level and application errors will show up here.
Some of the above may have changed under the newest macOS Sierra (which I'm not running).
