2) solar eclipse occurs on a new moon day and lunar eclipse on a full moon day.
When moon comes in between Sun and Earth, very little part on one side of Moon will be seen by people facing the Sun or Moon. Light reflected from other parts of Moon will go else where and not on to Earth. So it is a new moon day.
When moon is on one extreme of Earth with Sun on the other side, then the full circle of moon is visible to the people on the dark side of Earth (ie., night). The light reflected from entire moon reaches Earth at this time. So it is a full moon day.
When they are collinear in one line, the eclipse occurs. Otherwise, their orbits are such that they do not come in to one straight line, every 15 days.