One is a tool for processing holes from solid materials; the other is a tool for reprocessing existing holes in the workpiece.
Commonly used drill bits are twist drill, flat drill, center drill, deep hole drill and sleeve drill. Although reamers and countersinks cannot drill holes in solid materials, they are traditionally classified as drill bits.

The drill is a tool used to drill through holes or blind holes in solid materials, and can expand existing holes
According to the usage situation, there are hand reamer and machine reamer. Machine reamer can be divided into straight shank reamer and taper shank reamer. The hand type is straight.
There are many types of reamer according to different purposes, so there are many standards about reamer
The reamer is used to ream the hole after drilling (or reaming) on the workpiece, mainly to improve the processing accuracy of the hole and reduce the surface roughness. It is a tool for finishing and semi-finishing of holes , The machining allowance is generally very small, after the reamer processing