what is sex and how condoms are used in practical life tell

@ seema 
fertilisation is the other name of that , 
and that means the mating of female gamate OVA and the male gamate sperm , and they will fuse together in the ampullary – isthmic junction , and the sperm will going to fuse the ove . 
as far as condoms are considered , they are actually the barrier method , and used to prevent the STD ,  
and also helps in controlling the population . 
HOPE IT CLEARS 
ALL THE BEST ..