There are many different answers to this question, some presenting four pillars of Hip Hop, some five, some up to nine or ten elements of Hip Hop. For this guide, we will align with the definition used by the Universal Hip Hop Museum and center on five elements:

• DJing: Is the mixing of music and sound to entertain
• Emceeing: Emceeing or rapping is the vocal element of Hip Hop. This is used to tell stories, make music and entertain people.
• Breaking: This is the dance form of Hip Hop. Breaking is also known as Break Dancing which is the name the media has given to Breaking.
• Graffiti: Graffiti/writing is the visual art form of Hip Hop. It is used to tell stories and express the feelings of the artists.
• Knowledge: Knowledge is the fifth and often forgotten element of Hip Hop. Especially knowledge of self.

Source: CypherCure, Hip Hop History (this site also gives additional definitions for the five elements)