Male condoms are believed to be one of the safest and most effective birth control methods. They are 98% effective at avoiding pregnancy if used the right way. But if used incorrectly, they are only 85% effective. Female condoms are 95% effective at preventing pregnancy if used correctly. When used incorrectly, female condoms become only 79% effective.
Both male and female condoms additionally protect against STIs which get transmitted via body fluids such as semen, blood, and vaginal fluid.
So, there is no type of condom that is 100 percent effective. But condoms are the only method of protecting against getting STDs, provided they are used the right way. So, even if you are using other birth control methods, you still need condoms to prevent STDs.