The word Wahhabism comes from the Sunni Islam scholar and teacher Muhammad Ibn 'Abd Al-Wahhab who lived on the Arabian Peninsula during the 18th century. Wahhabism is a sub-branch of Salafism. An Ultra-Conservative religious movement within Sunni Islam (Fun fact: Ever seen a muslim with beard but not a moustache? That's a salafist).

Even though Wahhabism is a sub-group of Salafism there's differences between the two. Wahhabism is more violent and intolerant in nature. Wahhabism is critial to other Islamic movements and religious ideologies as well as other religions. There's no room for philosophical interpretation of the Quran everything is interpreted litellary. It's important to see the difference between true believers and infidels to better justify political expansion with use of force and violence against other muslims. Think of it like this: All Wahhabists are Salafist but not all Salafists are Wahhabists. Some Jihadi movements within Salafism see violence as the only option the spread the word of Allah, and some only use peaceful means. In Wahhabism violence is much more easy to use because of it's ideology.

During the 18th century Al-Wahhab went into a political alliance with Muhammad Ibn Saud and the Saud family. Together using their ideology as a Casus Belli they declared Jihad against other nearby muslim tribes, and conquered areas in what would be todays Saudi-Arabia. Because Saudi-Arabias religious establishment is based on Al-Wahhabs teachings, Wahhabism is strongly identified with Saudi's practice and exercise of Islam. Because of this Wahhabism is the foundation for modern day Islam and Salafism in Saudi-Arabia. Wahhabism is therefore used as the Saudi practice of Salafism.

Will provide sources if asked.

I apologize for any spelling and grammar mistakes