First, decide what you need the bike for. If you plan to ride it only around the city and parks at a walking pace, then a city bike, or cruiser will suit you. It is quite heavy, with a minimum number of speeds, mainly with a low "female" frame, an almost vertical fit, slight cushioning, a wide comfortable saddle and a boot or basket for things. It is better to choose such a bike with wheels with a diameter of 28 inches - it will be inconvenient to ride it on rough terrain, but it is very comfortable to move around the city.
If you prefer to ride through the woods, park paths and other places with a harsher terrain than asphalt, then you should take a closer look at mountain bikes : they have wide wheels with a large tread for better grip, very sensitive brakes, several speeds and shock absorbers (bicycles with a front suspension fork are called hardtail , and with two suspensions - double-hanging ).
Two-gimbal absorbs the maximum number of strokes, and hardtail is more suitable for those who ride on rough terrain and on dug up city boulevards. These bikes are more reliable in operation, as they have fewer moving parts.
If you plan to drive on the highway, your option is road bike : faster, with thin, very lightweight wheels and a rigid fork (without pendants).