Roman citizens were divided into two classes, Plebeians and Patricians.
The patricians were the upper class. They were the wealthy land owners.
The plebeians were the lower class. They included everyone who was not a patrician. They were sometimes just called plebs. At one time, plebs were the poor people of ancient Rome. They were the workers. Plebeians and Patricians rarely mixed socially. (Slaves did not count in either group. Some slaves treated well, some treated not so well.)
In the beginning, their daily life was quite different:
For a while, it was illegal for a pleb and patrician to marry. Under the Republic, that law was finally changed. Still, marriages between the classes was rare.
Under the Empire, both classes were similar in what they could do. All free adult males were citizens, no matter what their class. In both classes, the oldest male was the paterfamilias or head of the family. Old age was honored, and women had no rights. If you could afford them, both classes owned slaves. The houses of both classes were designed the same way unless you were too poor to own your own home. Everyone worshipped the same gods. They observed the same festivals and holy days. Everyone spoke Latin and everyone went to the baths and enjoyed the forum.
In the beginning, under the Kingdom and probably under the Republic as well, classes dressed very differently. It was easy to tell who was a pleb and who was a patrician. This site has great pictures to show you the difference. Over time, the way plebs and patricians dressed became more similiar. Boys wore a tunic down to their knees. It was white, with a crimson border. Once a boy became a citizen at age 16 or 17, he put aside his childish clothes, and wore an all-white tunic. Roman girls wore a simple tunic with a belt at the waist. When they went outside, girls wore a second tunic that reached their feet.
In spite of the fact that over time the plebs were given equality under the law, there remained two distinctive social groups in ancient Rome - the plebeians (lower class) and the patricians (upper class.)