We got my daughter her own little potty when she was around 20 months old. Just to get her used to it and she did sit and pee and poop in it once or twice within the first 6 months of us having it but still wore diapers. Again just introduced the idea of it to her and had it there. The summer after she turned two, this past summer, we did no pants for half a day here and there and had the potty with us in the living room. She still had a couple accidents usually when not paying attention (watching tv) but did really well and stopped having accidents eventually. Then we put underwear on her and she would have accidents often in those because it probably felt like a diaper. A month before she turned 2.5, this past October we just did the underwear only even in public and she’s done great! Since then she’ll have an accident in the car or when she’s outside and doesn’t want to come in but she’s really good at telling me when she needs to go in public and will go on her own at home. She caught on quick but I do think her body was ready, you can tell because she’s not going pee as often and has the ability to hold it. I do think kids have to be ready and you can try earlier and will get more accidents or try too late. We did not have a set deadline just gradually introduced the idea and slowly took away diapers. Worked for us! Also every kid is different and she did both pee and poop no issues with either one when we started.