What is CFM


Cubic feet per minute (it's how much airflow a fan moves) it means more air being moved. But if you mean for a cpu cooler no cfm doesn't tell the whole story. If you blow a ton of air on a stock cooler it'll still cool like crap, conversely if you blow half the air on a good cooler (dnh15 or something) it'll cool better
CFM is the Cubic Feet per Minute = total air volume that a fan can move in open stand on max speed.
while important, most fans are not used in open stands and on max speed.
So this metric alone is not informative.
If you want to ask "which fan is better for...", post the fans models and purpose (for example case fan, radiator fan etc.)
Fans don't cool, they move air.
CFM represents the max volume that can be moved by a fan at max speed without any restriction.
think of it as HP for an engine. engines also have torque value. in fans it would be Static Pressure which defines how good the fan at overcoming airflow restrictions.
And of course there is a noise and RPM factors.
So to decide which fan will suite your needs, it would be helpful to answer questions like
where the fan would be used (on a cooler, on a radiator on a case)?
how much of airflow restriction in that environment ?
are there noise preferences?
what size of the fan is required?
how much it should cost ?
some people would consider color and lightning options of the fan.
with all that info, you can make a new thread and someone will help you.