Six (Muslim-majority) countries are on the list. People from these countries will not easily enter the U.S. for the time being.
However, if people have a "bonafide connection" they can enter. That means people with mothers, fathers, siblings, significant others, and even step-siblings. A grandparent or grandchild, though, can't get in.
People with work, even a prospective job or to give a lecture or something, can enter.
All those who have applied for visas and are waiting, we don't know yet what will happen to them.
It will be tougher for refugees from these countries as well, if they don't have close family ties in the U.S.