A government shutdown in the United States occurs when there is a lap in appropriations, e.g. the government has run out of money. In the case of the shutdowns in both 2013 under Obama, and on the anniversary of President Trump’s inauguration in 2018, this was because Congress failed to pass a budget. In the case of the 2018 shutdown, Congress had been operating on a series of short term spending agreements after the last budget expired in spring 2017. The Congress opted not pass a regular appropriation bill, which would have covered the financial year (1 Oct. to 31 Sept. of the next year). Instead, Congress passed a series of continuing resolutions, the short-term spending agreements mentioned above.
On 22 January the Senate passed another continuing resolution, funding the government for 17 days. The Senate minority leader, Senator Chuck Schumer (D-NY), agreed to this deadline because the majority leader, Senator Mitch McConnell (R-KY), promised a vote on DACA before the expiration of this budget on 8 Feb. Senator Jeff Flake (R-AZ) voted for the 2017 Republican Tax Overhaul on a similar promise from McConnell, but there was no vote on a DACA deal after the President’s racist remarks in a January meeting about the bipartisan deal. Importantly, the 8 Feb. deadline falls before the date DACA recipients face deportation. Another shutdown is likely.