When a reader adds information that he or she already knows to what is stated, the reader is making an inference (Beech, 2005). In other words, the readers can make conclusion after reading the text.
For example: One day Aladdin and Mustafa walked in the desert and came to a cave. Mustafa was afraid to go inside the cave, so Aladdin went inside and found more riches alone. Did Aladdin enter the cave with Mustafa? No, he did not. Aladdin entered the cave alone (inference).

The inference or the conclusion from the sentences above is Aladdin entered the cave alone because from the sentences we can make the conclusion that Mustafa did not enter to the cave so, Aladdin entered the cave alone.