What kind of bike is this
Looks like a 70s/80s single-speed bike, or possibly a 3 speed rear internally geared hub at best.  Will be a steel frame and forks.  Those brake calipers look somewhat flimsy, and the plastic saddle is definitely non-original, possibly from a BMX or kids bike.

The cottered cranks are a really old design, which were common in the 60s and perhaps the 70s.

Its also possible it was a derailleur bike in the past but has had parts changed.  

Unless you know its history, it only has value as a daily ride or scrap metal