How much should you edit your images and what is ethical? Is sticking another person into a photo or worse, deleting a person, legitimate? In journalism, I think very little editing is legitimate, but for an artistic photom, anything is possible. Want to change the clouds that you got on that day of shooting? Change them.
Usually though, most people try to get the best photo possible on the day. Afterall, that’s the fun of it.
So what editors to use? There are hundreds of free photo editors out there but I do recommend buying two of them. If you cannot afford any of them, then GIMP is most like Photoshop.
I have recently bought Lightroom 5 and adore it. It deals with your RAW image (which has the most detail in it) in a much simpler way that Photoshop does, but then it doesn’t do everything that Photoshop does either. Lightroom is much cheaper than Photoshop which is also for graphic designers while Lightroom is just for photographers.
Here are some free tutorials on using Lightroom. You do not need to buy the CD. Just navigate down the bottom and you will see Free tutorials.
Don’t forget, you cannot save from Lightroom. You need to Export the edited image to another photo editor and then save it.
Adobe Photoshop CS6
Not so cheap, but the best
Adobe Photoshop Elements 11
Best for just photos and the cheapest, apart from the free ones, of course.