Hi Jessica!

Planets in the solar system receive the less sunlight the further they are away from the Sun. More rigorously the amount of the sunlight is inversely proportional to the square of the distance from the Sun.

Mars is further away from the Sun than the Earth so Mars receives less sunlight than the Earth. At the Earth the amount of sunlight received is about 1362 W/m^2 while on Mars the average amount of sunlight is about half of that, 600 W/m^2.

How bright the Sun will look at the planet's surface depends also on the composition of the planet's atmosphere. For example the atmosphere of Venus is very thick and it reflects a large part of the sunlight. Mars on the other hand has a thinner atmosphere than the Earth.