Oh, you're getting good. We like this question.
Your MA2ID is your unique account identifier. It's the bit that sits at the start of the domain you use to log into your Kulea account, so if, for instance, your login domain is https://acmeproducts.prod.kulea.marketing:8081, then your MA2ID would be acmeproducts.
Your MA2ID is yours and yours alone. You'll find a lot of third party applications require your MA2ID alongside your API key before they'll be able to talk to your Kulea account, so we highly recommend tattooing it onto your knuckles, alongside that 'I♥Kulea' tattoo that we know you have.