Forces always occur in pairs. Balanced forces are those forces that are equal in magnitude and opposite in direction and hence balance each other out. An example of a pair of balanced forces is a tug of war between two equal teams (in terms of strength). In such a case, each team will exert an almost equal force, but in opposite direction and hence net force would be zero and no team will win. Balanced forces do not cause change in direction or speed. If a body at rest is acted upon a pair of balanced forces, it will continue to be at rest. For example, if you were to push down a book on top of a table, this external force would be balanced by the reaction of table on the book and hence no change in the state of motion.
Unbalanced forces are those that have different magnitude and may or may not act in opposite directions. An example is a ball rolling on the ground (as a result of a gentle shove) will ultimately stop due to ground friction. These two forces (shove and friction) opposed each other and due to different magnitude caused a change in the velocity of object. Unbalanced forces may also cause a change in direction of motion.
Hope this helps.