There are four main types of infill: rectangular, triangular, wiggle and honeycomb (hexagonal).
Rectangular
The most common and general purpose infill. It’s often a default in printing software yet it offers no real structural benefit compared to some of the other infills.
Triangular
Triangular infills provide great strength, especially for high lateral loads. This infill is great to use when you print longer slender structures (such as bridges replicas, etc) or need good wall strength.
Wiggle
Wiggle infill should be used when you want your print to have a bit of flexibility and twist. It is the least rigid infill while still providing support.
Honeycomb (Hexagonal)
The most efficient and fastest to print, the go to infill for the majority of prints. It will it save material, time, energy and create high strength prints. Consider replacing your default rectangular infill with the honeycomb infill, your prints will thank you for it!