Irregular verbs are verbs that don't follow the regular pattern when forming their past simple and past participle forms. For example, "go" is an irregular verb, and its past form is "went" and past participle form is "gone" instead of "goed" and "goed". It's important to memorize these irregular forms since they don't follow the standard rules, and they are commonly used in English.
Select your English level (A1–C1) and download a free PDF worksheet with grammar exercises on Irregular Verbs.