Grammar errors are mistakes in the use of language rules that can affect clarity and understanding. These errors can include issues with sentence structure, punctuation, verb tense, and subject-verb agreement. For example, saying "She go to the store" instead of "She goes to the store" is a common grammar error. Correct grammar is important for effective communication, whether in writing or speaking. It helps convey the intended message clearly and professionally. Tools like grammar checkers and style guides can assist in identifying and correcting these errors, ensuring that the message is understood as intended.