The higher the number IE: 3:70, 4:10, 4:88 ect the faster the acceleration from a start and through the gears. The downside is that your top end speed will be reduced as the engine will reach max RPM at a slower speed than with a gear ratio of say 2:73
Also of note - deep gears or low gears have a higher numerical ratio (4.88 deeper than 2.73)
Taller gears use a lower numerical ratio (2.73 taller than 4.88)
Common slang - "adding gear" is in reference to going to a deeper gear (swapping a 2.73 out for a 4.88)
Taking away gear or removing gear is just the opposite.
Just in case someone is reading and isn't aware, the numbers are referencing how many times the driveshaft must rotate in order to rotate the tires once. IE - it must rotate 2.73 times in order for the wheels to make 1 rotation.
You want to match the gear to the engine, transmission, and vehicle weight, as well as projected use for the vehicle, and tires... and your personal preferences.
A 2.73:1 gear would be a good versatile gear for an engine with plenty of low end torque, in a light vehicle, with a deep 1st gear and small (normal) street tires, and no overdrive, used mostly for cruising... IMO. Depending on the setup, you could spin tire or hook up, and still have low highway RPM without overdrive either way.