This is primarily beneficial to investors who may not wish to invest in the major search engine, but would rather see their money go toward's Google's (Alphabet's) medical research, smart cars, household devices, etc. The search engine will still maintain the name of Google, but the new parent company Alphabet will soon reside at http://abc.xyz.
This is probably a wise move for Google, who clearly lead the charge in all things digital and internet marketing. Being at the forefront of so many technological advances, it is going to be increasingly important for them to maintain a sense of transparency, not only for their investors but for the public. Reorganizing their empire should allow them to focus on using their resources efficiently and logically.
You may have heard about the hidden easter egg within Google's announcement. A discreetly linked period will send you to http://hooli.xyz, which is the "Google" of HBO's comedy, Silicon Valley. In the show, Hooli is known for its outragous inventions and ridiculous means of doing business. Google clearly has a sense of humor about all of this, once again making them appear a bit more humanized in a pretty robotic world.
To read the full announcement, check out what The Guardian had to say.