line jumping on execut gcode?

Hi Guys,
i have a generell question how the gcode prozessing works:

if i start running i gcode on linuxcnc, works it line after line? or is it or is it normal that there are some jumps (e.g. from line 72 to line 78 and then back to line 73)?

That depends on the G-code. Some G-code can have loop and branch instructions.

also if the gcode only consists G1, G2 and G3 lines?

Probably G4 too. You will only see the highlight on lines that actually take some time.

There are no G4 lines, I checked the code before i asked.