Okay, multiple answers.
1. A lot depends upon your camera, what you shoot (RAW or Jpeg), what you intend to do with your files, who interacts with them (are you submitting them for stock? Exchanging them with Creative Directors? Submitting them for contests?). And yes, your computer matters some. Also, be clear, you're often comparing Apples (no pun intended) to Oranges. Some programs (Mac's Photo, Lightroom) also manage photo collections. Affinity Photo, Luminar, Photoshop and many others do not.
2. The "standard" (in terms of what Creative Directors use, what most professionals use) would be Adobe Creative Suite (ie: PhotoShop). For some, they just use Lightroom. Adobe has, by far, the most number of plug-ins and programs written by third parties to work with Photoshop, it's not even close. The most videos and tutorials available. If you are looking to do this as a business (not personal portraits or maybe real estate but doing corporate portraits, working with creative directors), you need to go the Adobe route (and no, Lightroom won't be sufficient then).
3. Me, I use Affinity Photo. You don't pay a monthly subscription ala Adobe--buy it and all upgrades come with it. I love it. Powerful, very capable, lots of good videos, mediocre text material (if that's how you learn). FWIW, you can integrate AP in to your Mac Photos program (so you upload all photos in to Photos and then, when editing, call in AP for those shots that require some special attention and do it all in Photos). As others have mentioned, it's nondestructive. That means it creates a copy of the file and you work from the copy, not the original. And AP was originally written for Mac--they have a Windows version but it's been my "general" experience that programs originally written for one platform often tend to perform better than an alternative. If you don't want to pay a monthly rental fee, I highly recommend you take a look at AP. One other plus--it has two other separate programs for Graphic Designers and Text Production so if you do websites, vectors, documents or books, then AP will integrate seamlessly with that work.
4. I am not a master of GIMP. It is free. It is open source software (and for some people that's a decider). Lots of resource materials out there. A bit clunky. And like Photoshop, it's a bit of a bear to learn (though frankly, most people once they've learned a program go "it was easy" and any program they never mastered tend to say "impossible to learn.") Out of all the freeware programs, this one has the most supporting material (videos, courses, text). I have no idea how well any Photoshop plug-ins work with GIMP.
There are plenty of other programs out there. It's really a function of what type of editing do you want to do. If you play with layers, you really need to look at AP or Adobe. If you're just looking to crop, lighten, maybe add some contrast or color, you've got a lot of options.
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5. Your camera body (especially Nikon and Canon) will make basic software that is often the best RAW conversion program (because it's designed for the RAW files of that camera brand) and usually does batch reviews and editing well. For instance, I rarely use the Nikon "Capture NX-D" except it's very useful for quickly loading 400 photos and then doing a quick scan as to what to keep and what to ditch. I can't comment on Canon's software--I use Nikon bodies. This software is free, download from the manufacturer's site and worth having as a backup if nothing else. Does very basic editing (light, crop, etc.).
6. Artificial Intelligence programs. We have entered the AI world and there are some AI programs out there you need to take a good, long, hard look at. They (based on what I know) aren't good enough to be a complete editor. But you need to consider having them to augment what you do use. Luminar gets great reviews--I don't have it so I'm just repeated what multiple people have told me. I'll just say you should look at it. I have Topaz Labs. I got it when 3 other photographers who's work I admire personally told me it was incredible. It's 3 separate programs. One is Gigapixel. It expands photos (adds pixels) so if you had to shoot something at ISO 64000 and want to blow it up or crop massively (for instance, I shot a snowy owl in complete darkness from a distance), I used Gigapixel to effectively make it look like I shot at ISO 2000. DeNoise is exactly what it sounds like--it removes noise. And Sharpen will sharpen up your photos (though I've found on the extreme ends it will add a lot of artifacts). I use one of these programs about 5% of the time when I edit--and they're indispensable, absolutely indispensable. They have saved a bunch of photos (where my DoF was too narrow and they expanded the DoF by adding focus). Or they turned a soft portrait into one that was sharper. My eyesight isn't as good as it used to be so there are sometimes for a professional portrait, the Sharpen program is a lifesaver.
And this isn't AI but while we're talking plug-ins and support programs (so you do basic edits in Program X like Lightroom or AP and then go to a second program because it doesn't something extraordinary), take a look at the Nik plug-ins. Extraordinary.
7. Last of all, there are some free editing programs (besides GIMP which has a steep learning curve) and the very basic programs by Nikon and Canon. They don't (IMO) hold a candle but the programs I've mentioned. But lots of people use them and they're free and if you're doing very basic edits (ie: not cloning, no layers, nothing sophisticated), then Bob's Your Uncle. Pixlr, Inpixio, Fotor, Darktable, Paint.net, and then some mobile apps (ie: only work on your phone) like Lightroom or Photoshop Express. Many of these also include ads (which is why they're "free").