What exactly it means to facilitate is part of what the court is considering. From the Vox article:

The Supreme Court concludes that the lower court’s order “properly requires the Government to ‘facilitate’ Abrego Garcia’s release from custody in El Salvador…

But it adds that the “intended scope of the term ‘effectuate’ in the District Court’s order” — to “facilitate and effectuate his return — “is, however, unclear, and may exceed the District Court’s authority.” The word “facilitate” suggests that the government must take what steps it can to make something happen, while the word “effectuate” suggests that it needs to actually make it happen.