Inferring is using your prior knowledge to figure something out
To infer start with trying to understand the image, for example if someone was trying to infer a few things about this image:
First, someone uses their prior knowledge, for example, someone might know this person is in a relay race. Someone would also know that this person has the legs in the ready position.
If people would know all of that then they would be able to make a inferring statement like this:
Someone is getting ready to run in a relay race.
L.I - To infer information no written in a text