Definition - What does 64-bit mean?
64-bit refers to the number of bits that can be processed or transmitted in parallel, or the number of bits used for single elements in data formats. It also refers to word sizes that define a certain class of computer architecture, buses, memory and CPU.
Techopedia explains 64-bit
In computer architecture, the 64-bit denotes those 64-bit integers, memory addresses, or other data units that are at most 64 bits or 8 octet wide. In microprocessors, 64 bits indicates the width of a register. A 64-bit microprocessor is able to process memory addresses and data represented by 64 bits.
A 64-bit register stores 264 = 18 446 744 073 709 551 616 different values.
The term can also be used to denote the size of low-level data types, such as 64-bit floating-point numbers.