Fundamentally, Republicans are conservative and Democrats are liberal. Democrats are on the left and Republicans are on the right. Sometimes they are called left-wing and right-wing.
In his farcical campaign for president in 1968, Pat Paulsen addressed the issue of right-wingers and left-wingers when he wrote: “I am neither right wing nor left wing, I am more or less middle-of-the-bird. I feel that if a political party leans too heavily toward the right wing or the left wing, it tends to fly around in circles.”