The name Decoder means to translate or decode coded information from one format into another. A binary decoder transforms n binary input signals into an equivalent code using $2$n outputs. For a $2$ to $4$ Binary Decoder, the decoder has two inputs namely A$,$ B$,$ and four outputsdenoted by Q$0,$ Q$1,$ Q$2,$ and Q$3.$ As you can see in the truth table $-$ for every input combination, one output line is turned on$.$ This decoder circuit can decode a $2-$bit binary number.