<CENTER ...> indicates a section that is centered.
<CENTER ...> is exactly equivalent to
<DIV ALIGN=CENTER>.
<CENTER ...> is being phased out. Use
<DIV ALIGN=CENTER> instead.
<CENTER>
Hi There! Let's talk about stuff!
</CENTER>
gives us
Hi There! Let's talk about stuff!
which is the same as
<DIV ALIGN=CENTER>
Hi There! Let's talk about stuff!
</DIV>