Sizing help!

I feel silly for asking this, but is anyone familiar with Carters sizes? Is 0-3 months the same as 3 months in other brands? And 3-6 months = 6 months? Some of my Carters clothes say 3 months on the tag, but when I go online to buy more it says 0-3 or 3-6, 6-9, etc and I’m confused. Also, is 24 months the same as 2T? Ugh why is this so confusing. Help!