ALG1 is based on your income over the past 12 months. It’s 60% of the monthly average.
ALG2 is based on your living expenses. It covers your rent plus 450-500€ depending on the number of dependants.
There are also some other benefits that one can apply for regardless of employment status, e.g. Household benefits (Wohngeld), which aims to help with covering rent with ~200€. Being eligible for these obv. requires being below a certain income threshold.
My expenses (rent, utilities and food) were pretty much covered. Obviously it wouldn’t cover a certain lifestyle, but I’m generally frugal, so I didn’t notice a difference.