Labor means work, task, toil. It is a word originating from the Latin "labore".
Labor is synonymous with toil, a arduous and prolonged work and the term is generally used for tasks of strength, manual work etc.
There is a difference between work and work, work is generally used when talking about an activity where the person feels the weight of work, it is a more difficult activity. Work, on the other hand, presupposes a rational activity, where the individual has to think, reason, it is work based on methods, strategies and not just physical, operational and suffered work.
In Latin, there is the expression "labor omnia vinciti", which means that work conquers all things, that is, work ennobles man, and makes people evolve, both professionally and personally, that they grow and learn many activities.
The United States celebrates Labor Day, or Labor Day, which is a holiday celebrated on the first Monday of September, unlike Brazil, which is celebrated on May 1st.