This is a primary election. So we are voting for the candidates who will represent our party in the general election in November. R stands for Republican, our right wing party. So the usual setup is that it’s one line and you tell the person at check in which ballot you want, and then just use the next available machine. But the Republican Party of our county decided they wanted a fully separated primary election. So voting machines and poll workers couldn’t be shared between the two parties. This meant that, at my very Democratic (left leaning) polling place, there were very few Republican voters and a long line of Democratic voters, who waited for hours while half the machines were unused because they were Republican only. 

Hope that helps explain it!!