You are following in a MN tradition of basically not reading up on stuff but just asking a daft question! Even if you're young, there's been loads of stuff on the broadcast media recently about the Queen.
For royals, it means:
Whether you like it or not, carrying out a role you didn't choose and may not be very well-suited to (shy, socially inept, perhaps insecure about your appearance etc). You will be scrutinised to hell and back in everything you do and often misunderstood and misinterpreted. You will have no come-back to criticism.
You will go and open things, make speeches, chat to endless folk, both people like me and you and state dignitaries. You must not put a foot wrong, forget names, or anything else. You must smile, look engaged and never show tiredness, boredom or irritation. Poor old Charles did that this week and got roasted for it. No-one will make any allowances for you as a human being, for sure.
I'm the sort of person who gets exhausted at too much social activity, but as a royal I might have several tasks of this sort each day.
You can't just go to the cinema, theatre etc when you want - ever.
It's a life-sentence.
I think it's an important role, when done well, as the last monarch. Soft power is hugely, hugely important in international relations...but to appreciate that, you need to read up in detail - esp the visit to Ireland in 2011, for example.
Also, there was a lovely thread on here yesterday sneering at the 'ugliness' of several members of the RF. Charming! Luckily, it was directed at the men (none of whom are ugly by any standard, whatever 'ugly' means). Thank Christ it wasn't about the women - that would never have been allowed.