Biden Title IX rules set to protect trans students - The Washington Post

Kinda, yeah. They are called executive orders and are basically a system formed because Congress didn't want to actually pass laws sometimes.

https://en.wikipedia.org/wiki/Executive_order

Title IX prohibits schools from receiving federal funding if they discriminate based on s*x. Congress directed each agency administering those programs to make regulations that govern how schools apply, show their compliance with the law, and can be terminated if they're found not to comply. The President has this power (and obligation) because Congress gave it to him—though to some extent, interpreting what the law means is a necessary part of executing any law.

Even though regulations have to be based on the law that Congress passed to be valid, the courts have long given a lot of deference to agency interpretations of the law, so it's rare for them to be struck down for that reason. Changing this standard is a pet project for groups like the Federalist Society.

Can the president just change this title anytime he feels like it?

There are legal procedures he has to follow for regulations to be valid (and this generates a lot of lawsuits, sometimes with the aim of delaying implementation until after the election), but in the end yes, it's pretty much the President's choice.