Purpose of Strange pcb track

[Vindhyachal.takniki]

I have attached some of PCB's showing strange PCb track. (zoom out file to 50% for clarity).

What is their purpose. Shouldn't they be straight way connected?

[ataradov]

A very typical trace length matching.

[Psi]

It's either to get a specific resistance or to adjust the delay in a signal bus so all the signals arrive at the same time.

[JacquesBBB]

This is to have a precise delay  in the transmission of the signal.

[Falcon69]

i always wondered what that was about. i see them all the time on computer motherboards.

[Psi]

Yep, when dealing with GHz parallel buses it doesn't take much difference in track length before some of the bits from one clock cycle arrive too late, which, as you can imagine, causes some issues 

[Vindhyachal.takniki]

It is very fast DIO board (upto 50Mhz).
I have noticed that tracks which had small distance between them, only those where made wiggled.
Tracks which had large distance very straight lines.

So I think correct reason would be
This is done to have signals to arrive at the same time at the end of the line.

[ataradov]

Tracks that run in parallel close to each other are differential pairs, to the length alignment is necessary to ensure that the signal in two wires travels the same distance and arrives with the same delay.

[c4757p]

I doubt those are differential pairs...

[ataradov]

It looks like the place that is show on the picture is the part where they have already been separated. Although they do look strange. There seems to be plenty of space here to keep them running in parallel.