A drill moves up and down, plunging into the material. A router moves horizontally and cuts a path within (or along the edge of) the material. A drill should not have horizontal forces applied to it, and a router doesn't make a good drill.
That said, like Vyger suggests, this is a question that should have been Googled first.
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And you can't use a regular drill bit in a router. A router also spins way faster, and according to the Youtube videos that I watch, they are extremely loud!
With your woodwork I'm surprised..
A drill is variable speed with a penetrating (Hole) sinking bit and a universal series motor if corded or a PWM DC motor if portable..
A router is a high speed linear edging shape pattern electric tool that could be an AC brush motor or better a two pole induction machine...
Google is your friend, try it.