An inference is drawn when evidence hints at a conclusion. It is not directly stated within the evidence but is reasonable guess based on the evidence provided. It isn’t a random guess or assumption. There has to be evidence to draw the inference. For example, if you saw animal prints in the snow, it could lead to the inference that a deer passed by recently.
The term inference is also used in story writing. If a character stops smiling, starts trembling, clenches their fist and turns red, the inference may be that the person is angry.