...

What is a plunge router tool?
A plunge router is a standard router attached to a plunging base that allows the bit to be lowered to a preset depth into a piece of wood. Typically, you'll want to use special plunge bits to make these cuts smoothly. 

Can you plunge cut on a router table?
The best way to do plunge cuts on a router table is to detach the router from its fixed position underneath the table, then attach it to a compatible plunge base and use it as a plunge router. Other methods can be unsafe and hard to control.

How do you cut a groove with a plunge router?
Mark and measure where you want to make the groove, set the router depth to how deep you want to make the groove, secure the wood you'll be working on with clamps, plus a piece of scrap wood to guide your cut so it remains straight. When you're cutting, make sure to pull the router slowly for smooth results and to prevent tearing.