If I make an image with all the partitions to the second drive, is it going to copy *ALL* of my data(including folders and files) and my entire OS installation?
Yes, assuming you choose the correct partitions when making the image file, which is easily done. If data is on a D partition, it's up to you to include D if desired. I do NOT include my data partition as I backup data through other means. I include only the partitions needed to restore Windows and installed applications. If you are like most users, you probably keep data, installed applications, and Windows on the same C partition and you would most likely include ALL of the partitions on your primary drive in the image file. Not just C. There is a checkbox choice in the Macrium interface to "include all of the partitions required to backup and restore Windows". That's probably what you'd do. That would automatically include C and the 2 or 3 other necessary partitions. I instead choose all partitions manually with individual checkboxes.
But, it's your responsibility to choose the desired partitions. Through menus and check boxes.
That would create one file, named something like qeta4et6s355tertstr7setetaetaet.mrimg. Macrium makes the name. Think of it as a representation of the files and folders in the chosen partitions, something like a single zip file that contains thousands of pictures.
You can save it anywhere you want other than on one of the partitions included in the image file. You can't save it on C if the C partition is in the image file.
That file would include whatever was in the partitions you chose to include in the image. Your pictures of your cat are in that representation IF the cat pictures are in a chosen partition. Your installation of Photoshop is in that representation IF that installation is in a chosen partition. Etc, etc, to include your spaghetti recipes and your Windows installation.
But that file is NOT bootable. If you poked it with your mouse, it would open up in File Explorer and you could navigate to your cat pictures and restore them if they had been accidentally deleted. But individual file recovery is not why people normally make an image.
If so, how do I get the backup drive up and running, if the main C drive crashes and is no longer usable at all?
You "restore" that .mrimg file to whatever drive you choose. Until you do that, the .mrimg file isn't of much use other than allowing you to fish around in it for your cat pictures.
Restoration is a formal process done within Macrium. After restoration, the drive to which the restore was targeted becomes bootable, assuming you chose the partitions necessary to restore Windows when you made the image file. If the image file contained only a data partition, then of course a restoration of that image file will not restore Windows.
Typically, to restore you would boot from the USB flash drive "recovery media" you should make within Macrium right after you installed Macrium. You would see the Macrium interface. You would issue commands with the mouse and menus, directing Macrium to restore an .mrimg file you choose to whatever drive you choose. That can be a brand new drive or an existing drive that you believe is in working order.
You should confirm that the "recovery media" will in fact boot your PC. It might not. Find out immediately after you make it.
If your primary drive is still bootable and in good working order, you could boot from it, open Macrium on your hard drive, and restore the image file without using the USB flash drive method. For instance, that might be what you'd do if you got in a minor jam and wanted to go back in time to last week when you made the most recent image. Rather than trying to use System Restore or doing a bunch of trouble-shooting.
How do I get to where the backup drive is bootable and running the same and the C drive? This is where things get confusing for me.
See above.
Do you have a typical installation, with installed programs, Windows, and data all on C? Some people install programs somewhere other than C. Many people save data elsewhere.
As far as I know, an image file can't include partitions from 2 different drives. My Windows and installed programs are on a Crucial SSD, while my data is on an Intel SSD. No problem, I don't image the Intel drive. I back up data WITHOUT using imaging. I make just one image file (monthly), containing ALL partitions on the Crucial. That's all I need to restore Windows, applications, and anything else that happens to be on the Crucial. That restoration would of course NOT include any changes made to my system AFTER the image file was made. It's a bit stale, but I can live with that. You might make image files weekly or even daily if you are highly concerned with the stale issue.