Word automatically checks spelling and grammar, and marks misspelled words with a red squiggly underline. Grammatical glitches get a blue double underline.
Try it: Put your cursor at the end of this paragraph, and hit Enter to start a new paragraph. Write a sentence with some spelling or grammatical mistakes, and press Enter to finish the paragraph.
Right-click the text that’s marked with underlines, or Press F7. Choose a suggestion to correct the mistakes.