If you look at your activity page ("suggestions" sub-tab), you will notice there is a list of suggested edits you have done; if you click on the "suggested edit" link, you will see the details about the suggested edits, including (for rejected edits) the rejecting reason, something similar to:
The "edit is too minor" is generally the rejecting reason. If you are going to edit a post, you should edit as much as possible of that edit, to avoid somebody else needs to edit again that same posts. The reason is said in this answer:
1.You can do better, always. The edit suggestion system teaches you how to edit, and editing more that just one typo is a good practice.
- Processing edit suggestions is not a free process, it cost eyes, distraction and time. We want quality in the queue, so high standards is a good first step.
The last point is also the reason why who don't have the privilege of editing any post is not able to suggest a single character edit.
To what reported in that answer, I will add that posts edited from 5 different users, or edited 10 times by the OP, are transformed in Community Wiki automatically. This is another reason for making the edits more substantial, and possibly resolve every issue present in the post being edited.
When you see that the suggested edit has been approved from Community, it means the suggested edit has been improved, which means there was probably something else that should have been edited.