I will attempt to answer this question by initially explaining what Hobbes' view on humanity was, since these views were what caused him to write his theory on the social contract, quote part of what he wrote regarding the subject and what it means in layman's terms
What Hobbes believed:
Thomas Hobbes, a 17th century British philosopher, had a rather pessimistic (but, in my opinion, not untrue) view on humanity. In a nutshell, he believed that humanity was born evil and needed society and law to keep it in order. Hobbes wrote that "during the time men live without a common power to keep them all in awe, they are in that condition which is called war; and such a war as is of every man against every man". In this state any person has a natural right to do anything to preserve his own liberty or safety, and life is "solitary, poor, nasty, brutish, and short." He believed that in the international arena, states behave as individuals do in a state of nature.
Within the state of nature, according to Hobbes, there is no injustice, since there is no law, excepting certain natural precepts, the first of which is "that every man ought to endeavour peace, as far as he has hope of obtaining it"; and the second is "that a man be willing, when others are so too, as far forth as for peace and defence of himself he shall think it necessary, to lay down this right to all things; and be contented with so much liberty against other men as he would allow other men against himself". From this, Hobbes develops the way out of the state of nature into civil government by mutual contract.
Hobbes coins a Latin phrase, Bellum omnium contra omnes, meaning "the war of all against all", and this is the description that he gives to human existence in the state of nature thought experiment that he conducts in De Cive (1642) and Leviathan (1651). To prove that this state of nature is a state of war, Hobbes begins with four assumptions listed below:
1) Natural Equality - People are roughly equal in their mental and physical powers. No one is individually radically superior in strength or cunning
2) Scarcity - The supply of many commodities is not large enough to satisfy the desires of all who want them. Imagine two people both want the same thing. This thing can't be shared, so obviously this will create conflict between the two people who demand this object. In an extreme case, the only way that one person will obtain the object is to "remove" the other person.
3) Equality of need - People, if they are at least minimally rational, are all concerned with their own long-term well-being. They care about the satisfaction of their future, as well as present desires, and strongly desire to prolong their lives. Since we all need the same basic things to survive, this may create conflict.
4) Limited Altruism - Individuals value their own survival and well-being much more highly that the survival and well-being of others. Even if people are not completely selfish, they nevertheless care very much about themselves; and you cannot simply assume that whenever your vital interests conflict with their vital interests, they will step aside. Almost no one will be willing to forego the satisfaction of his or her needs in favour of others.
What Hobbes proposed:
"The only way to secure self-preservation is to set up a certain kind of commonwealth by social contract that involves the “real unity of them all.”
The only way to erect such a common power, as may be able to defend them from the invasion of foreigners, and the injuries of one another, and thereby to secure them in such sort as that by their own industry and by the fruits of the earth they may nourish themselves and live contentedly, is to confer all their power and strength upon one man, or upon one assembly of men, that may reduce all their wills, by plurality...