MSB stands for Most Significant Bit.
In a multi-bit binary number, the MSB is the bit with the largest value. It is the one farthest to the left in the string.
For example, the MSB in the binary number 10101010 is the “1” to the far left.
In Embedded Systems the MSB is especially important when it comes to transmission of a data. MSB, together with LSB, is a key component of Endianness.