The historical significance of the latifundia is that their creation helped lead to social unrest in the later part of the Roman Republic.
The latifundia were large estates owned by riche landowners. They were formed by buying up land form small farmers or taking over government land. They were worked mainly by slaves and tenant laborers.
The development of these estates was a problem because it displaced people who used to be small farmers. These people then tended to gravitate to the cities where they helped to form a large urban lower class that could be very unstable and prone cause trouble in bad economic times. The presence of this underclass helped lead to turmoil such as that caused by the reforms of the Gracchi.