Well, we have two words here which mean very similar things.
Lazy which we know means someone who doesn't really work very hard,
but also one with a very similar meaning, idle. That's idle – i.d.l.e.
Both words can actually be used to describe someone who doesn't work very hard,
so, for example, "John is really lazy." or "John is really idle."
Both mean that really John doesn't work as much as he should do.
However, there are some very subtle differences between the two words which means we can't use them completely interchangeably.
For example, "lazy" will always have a negative connotation;
it will give us a very negative idea of the person it's being used to describe.
So lazy is always seen as a very bad thing.
However, idle can be used in other contexts, still to mean something or someone doesn't work, but without the negative judgement.
So for example, if you press print on your computer, you may see a sign which says "Printer idle."
This means that the printer, at the moment, isn't doing anything.
Similarly, sometimes factories must close, because there isn't enough work, and so at that point, the factory is idle.
And also, the work force, the people are idle.
So when we use idle in this way, we are not giving a negative comment on the people or the thing,
we are just saying they're not working.
Remember, when we say someone is lazy, we mean they don't work very hard,
but we can't say the printer is lazy, we can only say the printer is idle.