Are positive feedback and negative feedback similar? I don't quite understand if there is a difference.?

Positive and negative feedback systems are not really similar because they intend for different responses.  Positive feedback amplifies a response, whereas a negative feedback reduces the effect of something.

For instance, contractions that are experienced during childbirth increase in severity because of the hormone oxytocin.  Oxytocin is originally released, causing contractions, which cause more oxytocin to be released, and therefore cause yet more contractions.  On the other hand, negative feedback aims to have a more stabilizing effects.

Humans maintain homeostasis, for example, using negative feedback.  Another example would be maintaining blood glucose levels.  When it gets too high, the body releases insulin in order to store glucose in the form of glycogen (removing it from the blood), and if it gets to low, the body releases glucagon to convert stored glycogen into glucose to be released into the bloodstream.