All: We use "all" when we are talking about everything or everyone together as a group.
Example: "All the students are in the classroom."
Every: We use "every" when we talk about each individual thing or person in a group, one at a time.
Example: "Every student in the class has a book."
Each: We use "each" to show that something is done or given individually, one by one, and it's often used when you want to emphasize that you are talking about individual things within a group.
Example: "She gave a gift to each of her students."
"All" emphasizes that every student as a group is in the classroom.
"Every" emphasizes that each individual student is in the classroom.
"Each" emphasizes that she gave something to each individual student, one by one.