WASHINGTON - The Supreme Court of the United States made some big decision Monday.

Most notably was letting the Trump administration mostly enforce its 90-day ban on travelers from six mostly Muslim countries. The ban would apply to citizens of Iran, Libya, Somalia, Sudan, Syria and Yemen. The justices will hear arguments in the case in October.

The court will also hear a case about a baker in Colorado who refused to make a wedding cake for a same-sex couple. The argument here? Laws requiring businesses not to discriminate against LGBTQ couples violates their right to religious freedom.

The Supreme Court has also ruled that churches have the same right as other charitable groups to seek state money for new playground surfaces and other non-religious needs. The justices on Monday ruled 7-2 in favor of Trinity Lutheran Church of Columbia, Missouri. The church sought a grant to put a soft surface on its preschool playground, but was denied any money even though its application was ranked fifth out of 44 submissions.

The high court also announced a handful of cases they will not hear. They include a case that questions whether a person's constitutional right to keep firearms for self-defense extends outside of the home. The justices also rejected a case asking to loosen the rules around convicted felons possessing firearms.

So how does SCOTUS decide which case to hear? University of Minnesota Law Professor Jill Hasday says unlike Supreme Court opinions, which are well written and argued on both sides, and literally ran out into the public for all to read... the decisions about which cases are heard are made behind closed doors and stay there.

Just four of nine justices have to vote 'Yes' to take a case and Hasday says most votes are likely quick because of the sheer math involved. Each year, there are roughly 7,000 cases that petition the court trying to be heard. They only take between 100 and 150.

There are a few criteria they also consider including if there are disagreements between lower courts or if they believe there was an error with a lower court's ruling. Also, if they just think it's a very important question.