Vibrational frequency is defined as the rate that atoms and sub-particles vibrate. Everything that we know as matter is constantly vibrating at a certain frequency; such that some things have high frequencies and others have low frequencies. The higher a vibrational frequency is, the closer it is to the frequency of light. With this being said, literally everything has a vibrational frequency -- your phone, your laptop, your bed frame, your individual organs, your emotions, etc. The human brain vibrates at about 72-90 MHz, the human body vibrates around 62-78 MHz, disease in the human body begins at 58 MHz (cold and flu specifically at 57-60 MHz, the human body is receptive to cancer at 42 MHz, and death of the human body begins at 25 MHz. Shame has a frequency of 20 MHz, while anger has a frequency of 150 MHz. Beyond that, love vibrates at 500 MHz and joy at 540 MHz.
So to answer the question of 'why should I want to raise my vibration': lower vibrations are connected to death, illness, and ill emotions, whereas higher vibrations are connected to good health and positivity.
Now, lets discuss energy and vibration resonance. Most people will agree, from experience, that an individuals negativity (whether that be called a low vibration, bad vibes, etc.) can rub off on the people around them; just the same as the reverse, being positivity or good vibes. Sometimes we refer to this as the tone or mood of a room or situation. However, what constitutes the energy in a room or area? What is in the room or area. Just as a person, with good or bad vibes, will affect the mood or overall energetic vibration of a room, objects will as well because of the simple fact that everything has a vibrational frequency. Therefore, if you are in a room or area with high vibrational objects, such as nature or a room with essential oils being diffused and high-vibe crystals, your vibration will naturally raise because of the effects of the surrounding objects.
Here is a list of seven crystals that are some of my favorites. I have contained the list to seven such that each stone resonates with a specific chakra. The stones are in order by the chakra that they relate to; beginning at the crown chakra and concluding with the root chakra.
If you are unfamiliar with the chakra system, you can learn about it here.