What other types of energy are there? Why solar? Why not wind energy, nuclear energy, or hydropower?

That is a good question. There are a variety of types of energy, such as:

• Mechanical (like wind)
• Magnetic
• Electric
• Light
• Chemical (like fossil fuels)
• Gravitational (like hydropower)
• Nuclear
• Thermal (like geothermal)

This video talks about the benefits  of renewable energy sources. Check it out!

Solar energy is a good energy source because there is more than enough of it to meet our current energy needs and also gives us a lot of room to grow. It also causes less harm to the environment than many of the other technologies available and it isn't something we will run out of (unless the sun goes out, in which case we would be in a whole lot of trouble). Solar energy, also, is abundant in some of the most remote places to which it wouldn't make economic (or political) sense to build transmission lines. In some places, solar energy is going to be the most competitive technology. In other places, nuclear, hydro, or geothermal will be the most competitive. In many places, fossil fuels will reign for a while.

Now, on nuclear, hydro, and wind. 

A lot of people are afraid of nuclear because there is no good place to safely put the waste and problems with nuclear facilities could be very costly despite its cost benefits during normal operation and relative cleanliness.

Many of the good places for hydroelectric power plants have already been dammed and made into power plants. Also, with hydroelectric power, you are limited to places where water runs in an energetically favorable place, so it is not a competitive option in many parts of the world.

Wind power tends to harm bat and bird populations and many of the good places where wind farms would be viable already have wind farms in them. Also, wind power tends to be intermittent (come from time to time and is not continuous), which makes it more difficult to feed into a power grid. Batteries are needed. Furthermore, wind turbines are expensive to build and many people do not like how they look and sound, making political challenges significant.

Solar energy still has its own issues. For example, the costs of installation and panels are not sufficiently low in many places that they can compete with fossil fuels. Also, not all of the materials used in the production of solar cells are safe for the environment and often fossil fuels are used to produce the energy that is used to make the solar cells. Solar energy, also, provides energy at times of the day when less energy is needed, so that energy must be stored. We need better batteries to store this energy inexpensively and safely.