US President Donald Trump's announcement of his immigration policy priorities has thrown further doubt over the future of the US' 800,000 "Dreamers".

The plans, revealed by the White House in October, tie future legal protection of "Dreamer" immigrants to funding for Trump's controversial border wall with Mexico and increased spending on immigration enforcement officers.

Al Jazeera answers some of the key questions about some of those who may be facing deportation as a result of the US president's recent announcements.

Who are the Dreamers?

The Dreamers are some 800,000 undocumented immigrants who came to the US as children.

They have been permitted to stay in the country because of the Deferred Action for Childhood Arrivals (DACA) legislation introduced in 2012 by former US President Barack Obama.

Most Dreamers arrived in the US from Mexico and other parts of Central and South America. On average, they entered the US at the age of six-and-a-half. About 200,000 live in California; almost 115,000 are in Texas and more than 30,000 live in New York, according to US Immigration and Citizenship Services. Many also reside in Illinois and Florida.

What is DACA?

DACA, created by former US President Barack Obama in 2012, protects by law young immigrants who were mostly raised in the US but arrived in the country undocumented.

The programme protects Dreamers from deportation, granting them a two-year period of amnesty that can be extended with a work permit and social security number.

Recipients of the programme's safeguarding must have no criminal record, proof they were brought to the US before the age of 16, were under 31 years of age when the programme was launched, and be at least 15 years old when applying to invoke its protection.

READ MORE: Texas police arrest DACA recipients in Austin protest

Applicants must also be students, or have completed school or undertaken military service.

The application cost is nearly $500, and permits must be renewed every two years. The application and renewal process takes several weeks.

DACA does not give beneficiaries legal US residency. Those who pass the vetting process receive temporary reprieves from deportation and a temporary permission to work.

Why was DACA introduced?

DACA was created by Obama following intense pressure from advocates who wanted protections put in place for young immigrants who had been mostly raised in the US but lacked citizenship.

After repeated failures to pass the "Dream Act" - which would have provided a path to citizenship for those who later became DACA beneficiaries - the Obama administration revealed DACA on June 15, 2012.

What's impact do 'Dreamers' have on the US?

According to a study by the University of California, San Diego, Dreamers have had a positive impact on the US economy. Some 97 percent of DACA recipients are employed or in school. They open firms and buy cars and homes and are predicted to boost the US economy by $460bn over the next decade.

At least 72 percent of the top 25 Fortune 500 companies employ Dreamers, meaning that phasing out DACA will likely force big firms to spend time and cash recruiting new talent, Tom Wong, the author of the University of California study told Al Jazeera.

What does Trump say about DACA?

Trump promised to revoke the DACA legislation during the 2016 presidential election, as part of his vow to make cracking down on the US’ estimated 11 million undocumented immigrants a top priority of his administration.

In early September, the Trump administration moved to scrap the programme, giving Congress six months to come to a political solution before DACA officially ends.

In October, Trump sent Congress a list of immigration demands that he said must be tied to any legislation related to DACA.

The legislative agenda includes measures to ban immigrants from bringing extended family members to the US, constructing a border wall with Mexico and penalising the country's "sanctuary cities", those cities and states that that limit cooperation with federal immigration authorities in an effort to help reduce the number of deportations.

READ MORE: American dream fades for child immigrants under Trump

"These findings outline reforms that must be included as part of any legislation addressing the status of Deferred Action for Childhood Arrivals recipients," Trump wrote in a letter to Congress accompanying the list.

This follows Trump's announcement last month the White House would begin "an orderly, lawful wind down" of DACA.

As DACA was created by executive order, President Trump has the power to reverse the policy should he choose to do so.

Who is pushing back against Trump's policies?

Trump's recently announced immigration policy priorities have drawn criticism from political opponents and advocacy groups, as well as from some within Trump's own party.

Top democrats have rallied against the policy with Senate Minority Leader Chuck Schumer, and Congress Minority Leader Nancy Pelosi labelling Trump’s plans as "far beyond what is reasonable".

"The Administration can't be serious about compromise or helping the Dreamers if they begin with a list that is anathema to the Dreamers, to the immigrant community and to the vast majority of Americans," they said in a joint statement released Sunday.

"We told the President at our meeting that we were open to reasonable border security measures alongside the DREAM Act, but this … proposal fails to represent any attempt at compromise," they added.

What happens next?

The deadline for DACA recipients to renew their status and be granted two more years of stay in the US ended on September 7.

If Congress fails to negotiate an agreement based on Trump's new legislative measures, or unless the president changes his policy plans, DACA recipients, who were unable to renew their status, could face deportation as early as March 2018.