What's the difference?

Rocket Surgeon β˜†πŸ πŸŒˆ β€’ "Retired" nurse, studying for masters in microbiology. One 13yr old, two stepchildren 9 & 11, husband & I trying for our first. It`s been a long road, but an amazing trip.
Ok, so it's been a long time since I've gotten pregnant & I never noticed any implantation bleeding with any of those. (One was full term, 3 miscarriages.) Anyways, I'm currently late by almost a 1-2 weeks. This morning I woke up & had very light spotting, light pinkish brown. It lasted about half the day & then nothing else. Still a bfn on the pregnancy test today though. My question is, what's the difference between implantation bleeding & pre period spotting?