The 4x4 insert pattern is the most common bolt hole setup on snowboards, featuring two rows of inserts spaced 4cm apart both lengthwise and across the board. It's been the industry standard for decades, which means almost any binding you buy will mount right up without adapters or special hardware.
With 4x4, you can adjust your stance width in 1cm increments, which gives you plenty of options to dial in a comfortable position. For most riders, this level of adjustability is more than enough to find their sweet spot.
The main reason to consider a different pattern is if you're looking at Burton boards, which often use their Channel system for infinite micro-adjustment instead. But if you want maximum compatibility and don't need ultra-fine stance tuning, 4x4 is a solid, hassle-free choice. Just match it with standard four-hole binding discs and you're good to go.