Check out this site for an introduction to inferences &  some practice inferring!

As a result in learning, students should be able to make inferences, draw conclusions, and make generalizations about what you read, pointing out from where in the text you based that conclusion.

Students apply a wide range of strategies to comprehend, interpret, evaluate, and appreciate texts. They draw on their prior experience, their interactions with other readers and writers, their knowledge of word meaning and of other texts, their word identification strategies, and their understanding of textual features (e.g., sound-letter correspondence, sentence structure, context, graphics).