One of the main cuts in the Senate version of the AHCA is Medicaid. Senators want to cut Medicaid = stop the expansion of Medicaid. 

So what is Medicaid? 

Medicaid is a federal and state funded healthcare program that helps cover the costs of health services for low-income people in the U.S. States manage the program and have the power to control where that money goes toward and who is eligible. 

Now, just because you are a low-income person does not necessarily mean that you are qualified for Medicaid. There are other requirements, which is why sometimes you'll see people say that they don't make enough money but don't qualify for Medicaid. There are different categories of people who are eligible for Medicaid, such as low-income seniors and pregnant women. The details for each category varies from state to state.

Still confused? Worry not, I shall explain it another way below. 

Take a football player who is trying to get drafted onto an NFL team. Now the draft is created for those who want to pursue a professional career in football just how Medicaid is created to help those who are low-income. Continuing with the football analogy, let's say that all the teams in the NFL need a quarterback but each team in the NFL has their own requirements for what their quarterback needs to be. So the 49ers might have different specifications for their quarterback than the Redskins. Just how each state defines the categories to be eligible for Medicaid. And so some teams might reject this player because he doesn't fit their needs just how some people might not qualify for Medicaid in their state because they don't fit the requirements.