Could you please explain the difference between affect and effect?

These two words are often confused. The word "affect" (af ekt') is usually a verb meaning "to influence." In Psychology, an "affect" (af' ekt') is also a state of mind or body. Here are some examples of how the word "affect" can be used:

Her grades were affected due to a lack of sleep.

The new patient had an angry affect.

The word "effect" is usually a noun meaning "result." The following sentences show how "effect" can be used:

The medicine may have serious side effects.

The destruction of the building was effected by the detonation of a bomb.

In the second sentence, the bomb did not just "affect" (influence) the destruction of the building — it made the destruction happen.