there are inline engines(small cars),
v type engines (like v6 and v8),
and boxer engines (like in vw bugs)
or even rotary engines.
there are air cooled engines(also in vw bugs or lawn mowers)
and water cooled engines.
engines can be carbureted,
throttle body fuel injected(tbi),
port fuel injected(efi)
there are high compression engines (recommended to use 91 octane)
(10.2:1 compression ratio aka 150 psi cranking pressure)
low compression engines (recommended to use 87 octane)
(6.9:1 or 7.2:1 CR aka 101 psi to 105 psi cranking pressure)
there are turbo charged and super charged engines