Particle
desu
(slang, humorous, chiefly fandom slang) Used at the end of a sentence to imitate Japanese sentence structure.
However, desu may never come before the end of a sentence, and da is used exclusively to delineate subordinate clauses. Source: Internet
It can co-exist with the case markers listed above, and it overrides ga and (in most cases) o. : 私は寿司がいいです。 main Watashi wa sushi ga ii desu. Source: Internet
For example, Kochira wa Tanaka-san desu ( こちらは田中さんです main). kochira ("this") is the topic of the sentence, indicated by the particle wa. Source: Internet
For instance desu is more formal and polite than da. Source: Internet
However, desu may not always be a predicate. Source: Internet
Japanese sentences with copulas most often equate one thing with another, that is, they are of the form "A is B." Examples: : The difference between da and desu appears simple. Source: Internet