For a good overview of what the enclosures were and a description of the effects that they had, I would recommend reading the first couple of chapters of Karl Polanyi's The Great Transformation.

Essentially, in England before enclosures most peasants had a sort of communal or common land outside the village or town where everyone would herd their flock to graze and on which many of them would live. Nobody owned this land, and it could be used by all. But starting around the 1600s the nobility discovered it was more profitable for them in response to the growing textile industry to buy land and close it off to others so that they could extract the most profit from their land. The laws that allowed them to do this were known as enclosure acts. This destroyed the livelihoods of now landless peasants who depended on this open land, and who were at the same time legally prevented from leaving their villages in most cases to search for work elsewhere. So it led to a enormous swell in poverty because many were deprived of work and also deprived of the means to find work. This was a big social catastrophe and there was a lot of unrest during this period. At first they tried to pass laws forcing these peasants to work in poor houses and also tried to pass laws providing a sort of minimum income (Look at the Speenhamland and Elizabethan Poor laws for more detailed information) to prevent growing poverty, but neither solution worked. Eventually, laws were loosened and peasants were allowed greater freedom to migrate to industrial areas that had need of a greater supply of labor and the minimum income was abolished, allowing the formation of a modern labor market.