Electricity, the thing we all use but don’t really notice, has unexpectedly become a hot topic under President Trump.

Why it matters: His administration is mulling bailouts for coal and nuclear power plants in a questionable attempt to strengthen the electricity grid. Meanwhile, this winter’s cold snaps drove up New England’s power bills and Puerto Rico is still grappling with one of the world’s worst power outages. Here’s a primer + glossary to help light the way.

Energy vs. electricity

They’re not the same thing. Energy is the type of resource used to make electricity. Once they're in the power lines, electrons are the same regardless of whether they came from wind turbines or coal plants.

America’s electricity resource mix is increasingly diverse: Natural gas and coal are each about 30%, nuclear power 20%, and renewable energy makes up most of the rest.

The electricity grid

This is a catch-all phrase describing America’s electricity infrastructure, most visibly through the power lines you see along the road.

The grid isn’t monolithic. Several, mostly separate, power grids exist across the country. Within each grid, there are different types of markets. Some are set up in an auction-based system where electricity sources compete, and others are not.

Resilience and reliability

Resilience is the energy word du jour, with Energy Secretary Rick Perry emphasizing it as he seeks to help economically struggling coal and nuclear power plants. Reliability is a close semantic cousin. What these words actually mean depends on who you ask.

“We can’t even agree on how to pronounce it, resilience versus resiliency,” said Neil Chatterjee, a Republican commissioner of the independent Federal Energy Regulatory Commission, which oversees U.S. electricity infrastructure.

Chatterjee, who says resilience is the grammatically correct term, defines the terms this way: “Reliability is making sure when you hit the switch the lights come on. Resilience is making sure you can bounce back in the events when the lights go off.”

Intermittency and variability

These words capture what it means for electricity that the wind doesn’t always blow and the sun doesn’t always shine. Technology can store wind and solar energy so it can be deployed at other times, but it’s not broadly available yet.

The International Energy Agency, an intergovernmental research group, prefers variability over intermittency because it suggests more of a spectrum (i.e., solar panels still generate some power on a cloudy day).

Baseload power

This term is used to characterize electricity sources that can be steadily on, and form a base for consumer demand. Coal, nuclear power and natural gas fit this bill. It’s the term of choice for Perry and others backing policies that support coal and nuclear plants.

Some energy experts are increasingly saying this term is outdated because wind, solar and storage technologies are becoming bigger parts of the electricity mix. The IEA is also phasing it out, its analysts say.

Tony Clark, a former Republican FERC commissioner, says “dispatchable” is better because it captures to what degree a resource can be turned on to provide electricity.

Capacity vs. generation

This is one of electricity’s most common and consequential misunderstandings.

Capacity represents the maximum amount that a power plant can produce in theory at any given time, whereas generation is what is actually produced over a period of time.

A wind farm and nuclear plant can have the same capacity, but the latter produces far greater generation per year because it operates close to its maximum output most of the time and doesn’t rely on variable wind conditions.

“In 2016 and 2017, more renewable energy capacity was deployed than all other types of power plants combined, including nuclear, coal, gas and oil ... [B]ut in terms of generation, fossil fuels continue to provide about two-thirds of the global electricity supply each year.”

— Brent Wanner, International Energy Agency analyst

Retirement and premature retirement

You may have heard these terms with coal and nuclear plants lately, but they're both misleading. They're used to describe plants that shut down for a variety of reasons, such as not making money, not complying with environmental regulations or reaching the end of its service life. Closure or shutdown are better terms.

Premature retirement, especially, isn’t a thing at all, says Alison Silverstein, an independent consultant who led the Energy Department’s electricity study last year. “Premature is in the eye of the beholder.”

What did I miss? This is my second glossary installment, building off a more general energy and climate primer published in February. Email me ideas at amy@axios.com for the next round.