How 2 get my icons back on my computer?

Idk what happened to my computer ok! All of a sudden the icon's on my computer disappeared how come? Also you no when you turn your computer on & then put the password in & the the computer turns on the icon's are suppose 2 be there but there not ! how do i get them back..??? OMG i really need this fixed because i don't want to get in trouble! btw idk what category to place this in