EILI5- childcare flex elect.

Can someone explain to me how this works? I am about to adopt my foster child and will be losing my childcare subsidy. Income-wise I will no longer qualify for aid and this brings my childcare cost from about $500 to $1500. I guess I’m confused at what exactly the account is and how I use it to pay? Is it similar to an HSA? Any info is appreciated as the adoption process is overwhelming enough and I am at a loss.