yeah so I had previously thought there was just grower feed for meat birds and layer feed for egg birds, but obviously that's not the case.
There are all types of feed. The significant differences between them are protein percentages and calcium percentage.
All you have to do is read the instructions on the bag. Every manufacturer formulates their feed for a specific species, age and sex. They always have feeding instructions so one knows what birds the product is intended to feed.
As you noted, the most common are starter/grower and layer feed.
But there is a meat bird feed for broilers.
Starter/grower is for all young chickens 'starting' and 'growing'.
There are also game bird starter (usually 28-30% protein) and game bird maintenance feed (about 13.5 % protein).
There are also waterfowl feeds that usually contain more niacin.
If someone is going to raise any type of livestock, it is imperative they understand the nutrient requirements of their chosen species and find a feed that contains those levels.
Just because a chicken is a female, that doesn't make her a layer. When she is actively laying, she becomes a layer. When she is still growing or takes a winter break, she is not a layer because she isn't building egg shells - hence the increase from 1% calcium in all other feeds to the 4% in layer feed.
When in doubt, read the instructions on the bag.