There are two common ways to put a door under electronic control, and they behave differently in the one situation that matters most, which is when the power goes out.
The magnetic lock
An electromagnet on the frame and a steel plate on the door. Energize it and it holds, with a great deal of force. Cut the power and it releases immediately.
That release behavior is called fail-safe, and it is the defining property. A maglock cannot hold a door during a power failure, by design. It also has no mechanical latch at all, so the door is held only by the magnet.
The electric strike
The door keeps its normal mechanical latch. The strike is the plate the latch sits in, and it releases electrically to let the latch through.
Strikes come in both behaviors. Fail-secure stays locked without power. Fail-safe unlocks without power. Which one a given door gets is a decision, and it should be a documented one rather than whatever the supplier had in stock.
The part that is not a preference
Doors in a means of egress are governed by fire and life-safety requirements, and those rules care a great deal about how a door behaves when a building loses power or a fire alarm activates. Maglocks in particular are normally required to be tied into the fire alarm and to have additional release arrangements at the door.
The specifics depend on the occupancy type, the local adopted code, and what the authority having jurisdiction actually enforces, and those vary. This is a genuine confirm-locally item, not a detail to settle from an article. Any installer who tells you a maglock arrangement is fine without reference to the code and the AHJ is guessing on your behalf.
Practical differences you will notice
A maglock needs the door to be well aligned to hold properly, and it holds a door that has no latch, which some people find unsettling. A strike works with the existing hardware and is often the smaller change to a door that already closes and latches well.
That last point is the one that decides most jobs. If the door does not currently close and latch reliably, no electronic hardware fixes that, and the first job is the door itself.
Power, backup and what happens in an outage
Both types need power, and what happens when it goes is a design decision rather than an accident.
A maglock releases and the door is open, which is safe for people and not at all secure. A fail-secure strike keeps the door locked, which is secure and means anyone inside is relying on the mechanical exit hardware to get out. That is normally exactly how it should work, and it is why the mechanical hardware matters as much as the electronics.
Battery backup changes the picture and should be sized deliberately. Backing up a maglock keeps a door secured through a short outage. It also means the door stays locked in a situation where losing power might have been the safer outcome, so it is a decision to make with the egress arrangement in front of you rather than separately.
Whatever is chosen, it should be tested by actually cutting the power and watching what the doors do. That test takes a few minutes at handover and is rarely done.
Elite Security checks that a door closes and latches as it should before putting anything electronic on it, and confirms the egress arrangement with the local authority rather than assuming it. More in the blog, or start with access control.