The IRS says that $600 stimulus checks have been sent.
The checks are from the last coronvirus relief bill. More than 147 million payments were sent out, this was a part of the bill passed in December.
Congress is currently working on another bill where there would be $1400 payments. Anyone who qualified for the $600 payment that did not receive it directly can claim it as a credit on their 2020 tax return.
More info at irs.gov