When you say something concisely, you use as few words as possible to get your meaning across. When you write concisely, you convey an idea briefly and straightforwardly.
The adverb concisely is useful when you want to describe a sentence, paragraph, essay, or speech that uses few words that are carefully chosen. Writing concisely is especially important in journalism, where writers need to clearly convey ideas and information. The Latin root word, concisus, means "cut off or brief," from concidere, "to cut off, cut up, or cut into pieces."