Around the world, roughly 168 million 5-17 year olds are child laborers (Child Facts). This is about 11% of the overall child population (Child Facts).
Not only this, but about half of all child laborers are involved in labor that in some way harms their mental or physical health or development (Child Facts). They may be involved in bonded labor, drug trafficking, sexual exploitation, and slavery (Child Facts). This is about 85 million children involved in dangerous labor (Child Facts).
And it is predicted that over 100 million children will still be involved in child labor by the year 2020 (Child Labour).
Child labor is everywhere. Unfortunately, it is hidden in places you might not expect. You can’t see the sweat of a malnourished child in the wrapper of a Hershey’s bar. You can’t feel the pain of a young slave in the material of the shirt you bought from Abercrombie. You may not even be aware that the things you buy are the products of child labor. But you may just be closing your eyes to the issue and pretending that it doesn’t exist. It’s not your fault. Companies that use child slaves make the suffering easy to forget. But child slavery is a problem that can’t be ignored forever. It is difficult to break the cycle of child labor, but it certainly isn’t impossible.

Source: US Uncut (http://usuncut.com/news/beware-of-these-10-popular-chocolate-brands-that-exploit-child-slaves/)
Often, children who are involved in child labor do not have access to education. Without an education, they cannot secure better jobs as adults, and will likely live in poverty as their parents did before them. When these people have children, their children may be forced to engage in child labor to bring in money, and will not be able to go to school. So the cycle of poverty continues, and fuels the cycle of child labor and slavery. Education is the most powerful tool in breaking this cycle.

Source: Slide Share (http://pt.slideshare.net/ritu10061988/causes-and-effects-of-child-labor)
There are many reasons why a child might become a child laborer. Children living in poverty may choose to become child laborers to bring in money for their families. Kids may work to pay off a debt owed by someone in their family. This type of labor is called bonded labor, and is illegal in many countries. A child could be forced to find a job if his parents fall ill or pass away, making the child the head of the household. (Child Labour)
Some children are also kidnapped or forced to work against their will. They might
be sold to someone who could utilize them for some form of labor.
Not all child laborers are enslaved or forced to take jobs at a young age, but for many children whose families are living in extreme poverty, getting a job to earn money might seem like the best choice.
There are also many forms of child labor and slavery. Agriculture is an industry in which child labor is pretty common. Children may harvest cotton, cocoa, tea, or a number of fruits and vegetables such as bananas and oranges. Child laborers may also be found working in factories, manufacturing products such as carpets, soccer balls, fireworks, clothing, glass, bricks, and surgical tools. Some children work in the mining industry, mining things like gold, emeralds, diamonds, charcoal, or chrome. Many child laborers work in domestic services, as maids. This is a particularly common job for young girls. Children may also work in hotels, shops, and restaurants. (What Is)
Then there are the children who work in the worst forms of child labor. These children may be involved in bonded labor, drug trafficking, prostitution, and slavery. (What Is)
The use of forced labor produces about $150 billion dollars of illegal profits every year. Billions of dollars are being made of of these exploited children. (Child Facts)