Direct Effect refers to the ability of an individual to directly invoke a legal norm in national proceedings: for example, the Union passes a regulation stating that everyone who is dismissed unfairly gets £2000 reward. An individual in a Member State is dismissed, and they don't get the £2000. The individual can then go to the court and directly rely on that regulation in court saying, I have a right under EU Law to £2000.
Indirect Effect is slightly more confusing to explain; indirect effect is where you go to court and rely indirectly on a provision of EU Law. You cannot go to the court and directly rely on it and invoke the legal instrument. Read up on the case law of Directives on this point, because I can't think of a good example.
In order for a norm to be directly effective, it must be directly applicable. Since the ruling in Van Gend / ENEL, the court has consistently held that the Union is a "new legal order" whereby the legal provisions are all directly applicable in Member States; they all flow into the national legal order without the need for a national implementing act (monoism). Only some provisions are then directly effective which is different, as I illustrated above.