I’m not at all confused.
I’ve been doing image acq for a very long time (from the days before digitized stock imagery used to come in a printed catalog with the comps on a CD, when you actually had to look at film negatives or color chromes.)
The professional terminology follows the evolution of the stock industry.
From High End too Low.
First comes Rights Managed imagery. These you pay a Royalty per specific use, either through filling out an online form or by contacting the owner/stock site directly. The license is very specific as to the number of impressions, the length of display, the size of the image on output, commercial or non-profit and any number of other modifiers to the price you will pay. These are usually also pro shots and various juried collections held by stock houses. It also includes sources not necessarily viewed as “stock” like a library, museum or direct contact with the Photographer. It also includes a lot of the Editorial Use Only imagery simply because if you want to use a recognizable piece of architecture or person’s image, that has to be negotiated.
Second is Royatly Free imagery, so-called because the one-time fee paid for this stock is not considered a “royalty” payment like the above. These are shot by semi-pro and amateur level photographers . On stock sites, they are usually vetted to some extent. You don’t see this payment option with non-stock sources. With Royalty Free, you pay for either a Standard or Extended License based on use, in either cash or by purchasing credits. The Extended License grants additional impressions or additional seats or whatever. Read both carefully and decide which is right. If what you want to do with the image isn’t covered under the EULA license, contact the stock site or owner directly. If this category includes editorial images, be very certain your use qualifies as editorial. Rights of Publicity will bite you in the butt. HARD.
Third is Free Stock imagery. These are strictly amateur photos and run the gamut from SLR to bad cellphone quality, though you will occasionally find altruistic pro shots in there. These are literally free for use, no fees or royalties, though often come with caveats. A lot of them are free for personal use, as in you can use them for your scrapbook, or print them on your home printer and put them on the wall. You may have to pay a fee for Commercial Use. If used in a design for a commercial or non-profit entity, that is a commercial use, even though you may be a hobbyist freelancer designer. Read the EULA carefully. Beware of Creative Commons licensing. There are varying levels of that, one of which says you can use it only if the subsequent work is also Creative Commons.
There is a level below Free Stock which doesn’t have a name, though I’d love to christen it PITA imagery. These are images found on websites, blogs, instagram, flickr, etc. where it is nearly impossible to contact the owner of the image to get a usage release. I particularly love the images that vanish after the webmaster has been contacted. Once had a whole site vanish.