“The Department of Homeland Security announced Wednesday night that it would pause deportations of certain noncitizens for 100 days starting on January 22”
…
“Given that immigration enforcement agencies have limited resources, presidents typically identify what classes of immigrants should be prioritized for deportation. Under former President Barack Obama, that included people who posed a threat to national security, immigrants convicted of serious crimes, and recent border crossers.
Trump essentially eliminated those priorities. The moratorium is supposed to give Biden a chance to reevaluate where the immigration agencies should dedicate their resources.”
…
“Noncitizens can still be deported if they have engaged in terrorism or espionage or are suspected of doing so, or if they otherwise pose a threat to national security. The head of US Immigration and Customs Enforcement can also intervene in an individual case to order their deportation.”
https://www.vox.com/policy-and-politics/2021/1/21/22241868/biden-deportation-moratorium-100-days