How do you determine if its your actual period or spotting?

Can we get pregnant even if we have our period? (thats IF we think its our period)
Just want to know the difference or how would i know if its spotting not a period?? does it always come in the same time as the expected date of period? what would spotting look like?
Because i know women mistakenly think that once they bleed, its menstrual period already. thank you!