When you first hear encoding and decoding, you may assume that these two words are the same, but actually, they are not the same. Encoding means that you are going to write down or encode different things.
For example, when you are placing details, this means that you are encoding the details. Decoding implies that you are trying to figure out something. For example, you are asked to analyze a page from a story. You should decode what the words in that page are trying to say. When you can figure out what the page means, this also signifies that you have successfully decoded it.