To summon means to call someone to come to you, especially with authority or urgency. When a principal summons a student to the office, it's not a casual invitation: it's an official call that expects a response. A judge summons witnesses to testify in court. A king in a medieval story might summon his knights to the castle for an important announcement.

The word carries a sense of power or formality. You wouldn't summon your friend to hang out after school; you'd just ask them. But a boss might summon an employee to a meeting, or a parent might summon children to dinner after calling repeatedly without getting an answer.

Summon also means to gather or call forth something from within yourself. A nervous actor might summon her courage before walking on stage. An exhausted marathon runner summons his last bit of energy for the final stretch. A student taking a difficult test might need to summon all her concentration and knowledge.

In fantasy stories, wizards often summon magical creatures or spirits, calling them forth to appear. This captures both meanings of the word: calling something to come to you, and bringing forth something that takes effort or power to produce.