Hip Hop and rap are related in some ways, because the two genres of music are interwoven. During hip-hop performance, rap can also be played. This does not mean, there is no difference between the two. Indeed, there are some differences. You can be singing hip-hop songs and there won't be a need for rap lines, likewise, you can be singing rap songs and it will completely rap song. But a meaningful hip-hop performance will always provide a place for rap lines.
Rap is like the vocal part of Hip Hop which usually moves with the song beat and rhythm. Hip Hop is a genre of music and Afro-American urban youth culture, which usually comes with rap music and a type of dance known as breakdancing. Hip Hop songs are widely known for this unusual beats and rhythms. Hip Hop beats are danceable. Those who sing rap songs, most times use rhymes and poems.