Reasons are explanations for actions. Eg. "The reason I was late turning in my homework is that I had to got to the hospital".

Excuses are explanations for actions (aka reasons) that are not socially justifiable. Eg. "The reason I was late turning in my homework is that my friends invited me out for drinks".

The hard part is that jackasses will view even valid reasons as excuses, because to them any factors negatively impacting you are not more important than the end result being achieved.

A reason is an explanation although not all explanations are reasonable.

An excuse is an attempt to justify a reason/explanation.

Excuses are used when the expiation is not reasonable.

I think this person asking you is really trying to tell you you did something the wrong way, but in a less direct manner, because directness is considered "rude" in some cultures.

The mistake here is that the person explaining is interested in things like being correct or promoting efficiency while the adversary is only interested in hierarchy and dominating the explainer within their social context. That's the miscommunication happening.

I really dislike rhetorical questions.

A reason is a motivation to do a thing. An excuse is a reason to do the wrong thing (though not necessarily an inherently wrong thing - just anything that the other person thinks was wrong).

More often than not it's more appropriate to say "I misunderstood, how should it have been done?" or "Sorry, I wasn't paying attention. I'll be more careful" which may or may not include an apology depending on whether you inconvenienced someone else.

excuses lend themselves to lengthy explanations. reasons are more succinct and pertinent

(got put in wrong place. Edited and put in correct place for proper response)