What is Rahu?
Rahu is a karmic node of the Moon. It represents chaos and spiritual change. Things that are smokey or not what they seem. He also rules over esoteric spiritual practices such as mantra and puja. There are always a purer form of the planets. It is like we have a relationship with them. Rahu is actually part of Ketu. Ketu was a demon that was cut in half by Vishnu. All of the planets were at a dinner to drink the elixer of immortality and Ketu snuck in. He had already drank the elixer, but Vishnu recognized him as a demon and cut him in half.
He then became Rahu and Ketu. Rahu is a head without a body and Ketu is a body without a head. Ketu represents what we have done in previous lives and Rahu represents where we have a lot of lessons, desires and things to accomplish. This is what we focus a lot on in this life but never brings us satisfaction. The karmic nodes also show trauma from previous lives. They behave differently if they are with different planets as well as in different houses and star signs.
As you can see astrology becomes complicated quickly which is why it is first best to focus on the yamas and niyamas. Create morality in your life. We need to follow the yamas and niyamas to be a good person. We need to follow them on a very high level to be a yogi. Focus on this and also on chanting the planetary mantras. Learn what actions in your chart are important to perform. Get a regular sadhana (daily practice) going. This is the best way to start.