An excuse may or may not be true. It's a reason for an apology.

Excuses are often used to justify or explain why someone did not meet expectations or fulfill a commitment. While some excuses may be valid reasons for not following through on something, others may be fabricated or exaggerated in order to avoid taking responsibility for one's actions. Ultimately, it is important to consider the validity of an excuse and whether it is a genuine reason for an apology or simply a way to avoid accountability.

Not necessarily. An excuse is a reason or explanation for something, especially one that is offered to avoid blame or responsibility. It is not necessarily true, and it is not always used to apologize. For example, someone might give an excuse for being late to work, even if they were not truly late.