Difference between indoor and outdoor WiFi Access Points

Yes, good outdoor APs often have several functional differences vs. indoor APs, besides enclosure and antenna. Although some fancy indoor APs may have many of these features, outdoor APs are much more likely to have the following features:

• Higher power built-in power amplifiers in their radios.
• Support for WDS.
• Support for proprietary wireless bridging protocols that use frame aggregation schemes to make more efficient use of long range wireless point-to-point links.
• More access to low-level radio tweaks, like tweaking the ACK timeout to adjust for the longer round-trip times of long-range links.
• Support for mesh schemes.
• Support for the 4.9GHz band, for licensed, often "public safety", applications.
• Support for Power over Ethernet so you don't have to run AC up the pole.

There's no operational difference between them.

That's like asking about the difference between indoor and outdoor laptops -- sure, one screen may be brighter or one's case might be weather-resistant, but inside they both work the same way.