What is meant by high-order and low-order bytes?

Lower order and higher-order bytes are the terms used while computing calculations in a programming language. Usually, numbers are written from left to right. The left is the most significant bit, and it is written first. For example, if we consider your paycheck, then you would be happier if the number the first digit increases instead of the last digit. This is what is referred to as "significance" of a digit. The bits present in computer memory are written usually with a base 2 (for binary, the base is considered as 2). So, the least significant bit is represented as one. The next bit is represented as two or 2'1 and the next one as 2'2'1 and so on.. For example, if we consider 2 bytes of memory, which represents a 16-bit number, then one byte will hold at least eight significant bits, and the other byte will hold the most significant 8 bits. The byte that contains the most significant 8 bits is called the higher-order byte and the one that contains the least significant bits is called the higher-order byte. read less

In Simple way : To understand High/Low-order bytes/bits, consider int as an example. int is 4 bytes in length. The 1st byte is the low-order byte, whereas the 4th byte is the high-order byte. This is the same for bits. For example, still using the int example, the 1st bit is the low-order bit, whereas the 32nd bit is the high-order bit. One Nibble is 4 bit's in length. 2 nibbles make a byte. The lower-order nibble is the first 4 bits. The last 4 bits is the higher-order nibble. read less