No worries
What it really means
Means "it's fine", "no problem" or "you're welcome". Used to reply to thanks, apologies or requests. "No bother" and "not a problem" mean the same.
Context, tips & common mistakes
No worries is the modern all-purpose social smoother, answering both 'thank you' ('no worries!') and 'sorry' ('no worries, honestly') — an Australian import so thoroughly naturalised that it now rivals 'no problem' and the older 'don't mention it'. 'No probs' is its texting form.
Its power for newcomers is symmetrical politeness on the cheap: when you hold the door, take an apology, or grant a small favour, 'no worries' closes the exchange warmly with zero effort. Note the related email usage — 'no worries if not!' softens a request by pre-authorising refusal, a very British construction. In formal writing, 'that's quite alright' or simply restructuring the sentence does the job instead.