The difference between layette lines and baby girl (or boy) lines is not too hard to grasp once you understand it. Layette sizes only go to size 24 months, usually starting at newborn or preemie or 0-3 months. Layette lines don't generally look like older kids' lines, although sometimes in the vintage years they did have a shared theme. Gymboree typically released three styles of layette: girls, boys, and gender neutral. Sometimes they were similar patterns, just different colors.
Baby lines almost always coordinate with the Kid lines, and also almost always have the same line name. Baby girl and boy sizes start at 3-6m, followed by 6-12m, 12-18m and 18-24m (or 12-24m), then (toddler) sizes of 2T, 3T, 4T, and 5T. Layette girl lines typically don't have accessories other than headbands, crib shoes, bibs, and blankets or animals.Baby girl lines usually have sandals or shoes, and hair clips, in addition to headbands.
Layette lines have tags that look different from baby girl/boy and kid girl/boy lines. Pastel tags are generally layette.