The word "Hakka" means 'guest families.' The pinyin (Chinese ideograms transliterated into the Roman alphabet) for Hakka is 'kejia.'
I am telling you this because I was surprised not many Chinese even know who or what Hakka is! The Hakka people in China acquired this name because in the past, Hakka families have had to migrate southwards within China due to plunderers from the North. There has been a total of four great Hakka migrations. Of course, now Hakka people are all over the world.
Hakka are most famous for their Hill Songs
Most Hakka people can speak either Cantonese or Mandarin so they do not speak a lot of Hakka. Not in public at least!
Hakka women are known for not binding their feet like other Chinese women in the past. During the migrations, they were known to take care of the safety of their families while the men were at battle.
Mandarin, Cantonese, Hakka, Wu, etc. are all Chinese languages and/or dialects. The reason they are lumped together as Chinese is because they all share the same written language. There is an interesting story about how the Emperor of China once destroyed all written forms of Chinese expect one to unify the Chinese language.
The majority of Hakka people in the world live in the Guangdong province of China. The capital city is Guangzhou. Hakka families outside of China can, in one way or the other, trace their ancestry back to Guangdong.