@Renata50......Renata, you may be a 'newbie' but you are anything but dumb! The fact that you asked this question means that are indeed a smart person.
Host cancellations are regarded as a serious breach of faith by Airbnb! When a guest books accommodation, they no doubt book other things that will tie in with that accommodation, like Air fares or other travel cost if they are coming a considerable distance.
Originally some hosts abused the booking system by cancelling a confirmed booking to chase a more lucrative one....a longer stay or similar and an element of mis-trust crept into the platform.
Airbnb have now introduced measures that make sure it is not equitable for a host to cancel a booking.
If you cancel a confirmed guest booking the following will happen......
1/. An automated posting will appear on your reviews will say 'The host cancelled this reservation *** days before arrival' and that will have an impact on your future enquiries. Guests tend to steer clear of hosts who cancel confirmed bookings.
2/. Your calendar will be blocked for the duration of the booking you cancelled, and you will not be able to accept a request for that period.
3/. A financial penalty (a fine if you like) will be taken from your future hostings and the size of that fine will depend on how close to the reservation you cancel!
4/. If you have Superhost status you will automatically loose it for a one year period from the date of the cancellation. If you do not have Superhost status you will not be eligible for that same one year period.
There are extenuating circumstances and if a serious enough event happens that will prevent you from following through with a reservation you MUST contact Airbnb, inform them of the event and ask them to relocate the guest. They are good at doing this and provided your reason for their intervention is sound enough you will be released without penalty!
But do not take it on yourself to cancel....it will cost you dearly if you do.
Good luck Renata.......and don't think of yourself as dumb.....ok
Cheers.....Rob