Determinism : Determinism is the view that every event, including human cognition, behavior, decision, and action, is causally determined by an unbroken chain of prior occurrences.[1] With numerous historical debates, many varieties and philosophical positions on the subject of determinism exist from traditions throughout the world.
Simple explanation: U are destined to do something, nothing will change..IF u could somehow know u going to die at age 100, nothing will change the fact
Free will:The question of free will is whether, and in what sense, rational agents exercise control over their actions and decisions. Addressing this question requires understanding the relationship between freedom and cause, and determining whether the laws of nature are causally deterministic. The various philosophical positions taken differ on whether all events are determined or not — determinism versus indeterminism — and also on whether freedom can coexist with determinism or not — compatibilism versus incompatibilism. So, for instance, 'hard determinists' argue that the universe is deterministic, and that this makes free will impossible.
The principle of free will has religious, ethical, and scientific implications. For example, in the religious realm, free will may imply that an omnipotent divinity does not assert its power over individual will and choices. In ethics, it may imply that individuals can be held morally accountable for their actions. In the scientific realm, it may imply that the actions of the body, including the brain and the mind, are not wholly determined by physical causality. The question of free will has been a central issue since the beginning of philosophical thought.
Simple explanation: ur destiny is on ur hand, ur fate cannot be determined by something

If you're talking about the religious aspect of free-will versus determinism...

Some say what we do has already been destined by God. Therefore, if what we do has been destined by God, then God cannot blame us for our sins because He is the one who has decided our actions, including sinning.

Some other people say that God gave us a free will, whereby we will have to follow what God wants us to do through the words of a prophet and/or a holy book and that we will be judged according to how we live our lives in the end times. Some say that a problem with that idea is that if it is true, then we should not be judged by people because God will judge us and since nobody is perfect, people should not judge us.

The debate for this is still on-going.