The Yellow Turban rebellion essentially started what ended up being the Three Kingdoms period (220-280). A lot of historians, including myself, mark it as the unofficial beginning to the Three Kingdoms era.

Before the rebellion there was a lot of tension in the Han dynasty because Emperor Ling enacted many policies that crippled government power and also spent a lot of the countries money on his luxury. The powerful Eunuchs (led by Zhang Rang) of the time gained high political power due to the corruption of the government.

The YTR gave opportunity for warlords such as Yuan Shao, Dong Zhuo, Cao Cao and Sun Jian to gain more prominence in military and government matters. The YTR itself wasn't actually very effective, due to the death of Zhang Jue not even a year into the beginning of the rebellion.

However, the YRT set off a chain of events. It made officials realize how corrupt the government was, and when He Jin went to put down the Eunuchs, he was killed which allowed Dong Zhuo to obtain power and control the puppet Emperor Xian who he had put on the thrown. This then resulted in a majority of warlords in the country to unite against Dong Zhuo to take back the capital and the Emperor.