Just to add for clarity, b is used for bits and B for bytes. Though they are often mixed up.
(... and a byte is not always 8 bits)
(... and a byte is not always 8 bits)
https://en.wikipedia.org/wiki/8b/10b_encoding
A byte is also referred to the smallest addressable unit. Which in most cases is 8 bits but many (I guess mostly niche architectures) have much larger characters/bytes, and is still very much relevant.
But probably for all practical purposes in modern era, we can safely assume it's always 8 bits.