The theme refers to the important and reoccurring idea in any text or artistic work. There are two ways by which the writer reveals the theme of the text. One is stated the theme and the other is implied a theme. In the stated theme, the main idea of the text is stated to the reader directly. In the case of the implied theme, the main idea of the text is extracted by studying the characters and events in the text.
A good discussion topic would be to not litter. Flies and bacteria arn't all bad though. If you see someone litter go pick it up and throw it at them and then dispose of it properly c: