PCs, laptops, Macs, Windows, phones and tablets - everything is 64-bit these days. Even some smartphones are 64-bit.
The main reason for the switch from 32-bit is to get past the limit on the amount of memory a 32-bit processor can access.
What is 32-bit and 64-bit?
Put simply, 32-bit is shorthand for a 32-bit number. This number contains 32 bits (binary digits) which are either 0 or 1. And example could be 10101010101010101010101010101010.
A 32-bit processor is - by definition - capable of dealing with instructions and referencing memory locations of 32-bits.
Why can't 32-bit CPUs use lots of RAM?
Given that each digit in the number can be only 1 or 0, the total number of combinations is 2^32, which is 4,294,967,295. And 4.29 billion memory locations (each storing one byte of data) equate to 4GB, which is why a 32-bit processor can access a maximum of 4GB of memory without some workarounds in software to address more.
4GB isn't really enough these days. It might be fine for basic tasks, but if you want to run multiple programs, have 35 tabs open in various web browsers or open 30 high-resolution photos for editing at once, 4GB isn't going to cut it.
And don't forget that consumer versions of 32-bit Windows can access only around 3.2GB even if 4GB is installed.
PCs, laptops and their operating systems are all 64-bit these days. 64-bit versions of Windows can access 8TB of RAM (that's 8000GB), while server versions can access 128TB.
These limits are explained in much more detail on Microsoft's website if you want to know more.
Give that today's PCs and laptops generally have 8, 16 or 32GB of RAM, we're nowhere near the limit of what a 64-bit processor can access.
What does x86 and x64 mean?
These are somewhat misleading terms, and are the equivalent of 32-bit v 64-bit.
x86 (or x86 architecture) has long been a common way to refer to the family of processors ending in 86, Intel's most successful line of processors. The first was the 8086, and many people will remember the 286, 386 and 486 processors in early PCs from the mid-1980s to 90s.