A helping verb (also called an auxiliary verb) is a verb that works alongside the main verb in a sentence to change its meaning or timing. Helping verbs don't carry the main action themselves. Instead, they help express when something happens, whether it might happen, or if it should happen.

The most common helping verbs are be, have, and do, plus words like will, would, can, could, should, may, and might. In the sentence “She is running to school,” is is the helping verb and running is the main verb. The helping verb is tells us the action is happening right now. Compare that to “She will run to school,” where the helping verb will tells us the action hasn't happened yet.

Helping verbs let you express ideas that would be impossible with just a main verb alone. You can show possibility: “It might rain.” You can show obligation: “You should study.” You can form questions: “Did you finish?” Without helping verbs, expressing these shades of meaning would require many more words.

Think of helping verbs as teammates for the main verb. The main verb describes the action, but the helping verb provides crucial information about that action: its timing, likelihood, or necessity.