What is mental phenomenon?

Every internal sense organ comes along with corresponding external organ. For example eye comes along with form, ear comes along with sound, nose comes along with smell , mind comes along with mental phenomenon. I am aware of the meaning of form or sight , sound , smell etc .. but I am not sure what is meant by mental phenomenon? When eye and form/sight come together eye consciousness arises. When nose and smell come to together nose consciousness arises. In both the statement above it is clear from my experience what is sight and smell. But when we say mind and mental phenomenon come together mind consciousness arises, it is not clear from my experience ,what is the mental phenomenon? Is mental pehnomenon the memory of past or the simulation of future or is it the dream or is it the speech ? There are different types of tastes ,colors ,odours, touch etc... Are there different types of mental phenomenon also?