(CNN) President Donald Trump declared a national emergency Friday afternoon over the coronavirus outbreak following a week of cancellations, suspensions and growing case numbers that unsettled Americans nationwide.

The move frees up billions of dollars in federal funds, Trump said, and sets the Federal Emergency Management Agency in motion.

The President invoked the Stafford Act, which is the statutory authority for "most federal disaster response activities." The Stafford Act gives access to the funds and the national emergency gives access to authorities, according to a person familiar.

Speaking in the White House Rose Garden, Trump said the action would "unleash the full power of the federal government."

Here's what to know about Trump's declaration:

What does a declaration do?

A declaration puts FEMA, which is supporting the Health and Human Services Department and the Centers for Disease Control and Prevention for coronavirus response, in a position to be a coordinator. In a statement Friday, FEMA said HHS will remain the lead agency directing the federal response.

The declaration makes more federal funds available along with supplies, personnel and other support. FEMA Administrator Peter Gaynor told lawmakers Wednesday that the agency's warehouses are stocked with commodities across the country.

Trump said Friday he was also urging every state to set up emergency operation centers "effective immediately" and asking "every hospital in the country to activate its emergency preparedness plan."

The emergency orders, he said, will also "confer broad new authorities" to Health and Human Services Secretary Alex Azar.

Azar will be able to "waive provisions of applicable laws and regulations to give doctors, hospitals - all hospitals -- and health care providers maximum flexibility to respond to the virus," he said. That includes waivers of some federal licensing requirements, waivers to critical access limits on numbers of beds and lengths of stays, and waivers to rules to bring additional physicians on board at certain hospitals.

When activated, FEMA might also help with logistics, like the transport of residents if needed, and put up temporary medical facilities. Those resources could come from across federal agencies, from stocked warehouses and through contracts. States will likely communicate what they need and where they need it.

Steve Reaves, president of the union that represents FEMA workers, said that during the California wildfires, for example, FEMA came in, put up tents, set up command and control centers, and worked with state and local governments to track casualties.

But during other health crises -- including Zika, H1N1 and SARS -- FEMA maintained a supporting role to HHS and declarations were never issued, according to Michael Coen, a senior adviser for emergency management at IEM and former FEMA chief of staff during the Obama administration.

"None of those became as big of an outbreak as we're seeing with COVID-19. But those were examples of FEMA being in support of HHS in some way, but without the use of a Stafford emergency declaration or major disaster declaration," he said.

Washington asked for a declaration on Thursday

Requests are generally made by the governor of an affected state. States have been scrambling to sort out what they need to respond to the increasing number of coronavirus cases before they make that request. During the week, FEMA personnel fielded questions from state staff about what support the agency -- which is within the Department of Homeland Security -- can provide to respond to the outbreak, said Reaves.

Washington Gov. Jay Inslee on Thursday requested that the administration declare a national emergency.

"It is incumbent on all of us to acknowledge the gravity of this public health emergency and take the necessary actions now -- not tomorrow, not next week -- to slow the spread of the virus and save lives," Inslee said in a statement Friday. "By declaring a national emergency, the federal government can provide states with direct assistance to meet our residents' needs for health care, shelter, food and cash assistance, and more."

Additional declarations might come later

Additional declarations might also be issued down the line, so the federal government can reimburse state and local governments for the costs incurred during an incident. For example, President Bill Clinton issued an emergency declaration in 2000 over the West Nile virus, authorizing millions of dollars in federal funds to reimburse affected local governments.

Declarations can start as one type of emergency and then change to another in order to access more resources.

Why did it take so long to declare?

Earlier this week, Senate Minority Leader Chuck Schumer, a New York Democrat, in conjunction with Sens. Patty Murray, a Democrat from Washington state, and Gary Peters, a Michigan Democrat, sent a letter asking Trump to "immediately" consider disaster declaration requests for the coronavirus.

The reason for the delay in proceeding with a request may have been because states were still assessing their resources and the federal assistance received thus far.

"It's possible that a) the states have the resources it needs b) that the state has most of the resources it needs and the resources it doesn't have it's getting from HHS and the $8.3 billion," said Daniel Kaniewski, who previously served as deputy administrator for resilience at FEMA.

"I think in the future if those -- and that future can be today or a week from now or it could be never -- if they require supplemental assistance beyond what they're getting from HHS, there would be an obvious time to submit an emergency declaration request," Kaniewski, who's now a managing director at Marsh & McLennan Companies, said.

New Jersey told CNN on Thursday, for example, that it hadn't reached that point. "Due to the recent release of more than $15 (million) in HHS funding that can be used for these COVID-19 costs, the State thresholds for FEMA assistance certainly have not been met yet," according to a statement from the governor's office Thursday.

As the crisis evolves, states will likely continue to review their needs and the role of federal assistance.