If you take PrEP every day, it is highly effective and provides a great deal of protection against HIV. The World Health Organisation and the US Centers for Disease Control say PrEP is over 90% effective. No prevention option is 100% effective.
PrEP does not treat or cure HIV.
PrEP is a new additional prevention option and is not meant to replace existing HIV prevention approaches if they work for you. It is one option among others such as using condoms consistently and correctly.