What are some popular, good, and free photo editing apps for iPhone?

I've been so lost! I've seen people's pictures, they look so beautiful and good! I've tried asking, but none of them reply. I'll give you some examples, in some pictures it's like mirrored and in others it had black or white thick side borders. Some of the pictures look a little grayed and they look smooth and clear, but they use their iPhones to do so! I've been really curious what photo apps there were, but free ones, since I can't use anymore money on it for a long time!

I'm sure they use instagram app for editing,
Power cam is a good app too
You can enhance a photo from your photo library without an editor by clicking edit, enhance

For effects I use pixlromatic, for the mirror type pictures I use picture effect magic, for Borders and such I use frametastic because you can do collages as well and you can change the color of the border and the size.

For the borders use whitagram and squareready. For the smoothed look get pixlromatic. Also try phonto.