In short, SMITE is a multi-platform free-to-play MOBA (Multiplayer Online Battle Arena) - a team vs team game where you play matches (usually 20 to 50 minutes) as gods/deities from various mythologies on a small, rather symmetric map with the usual goal to destroy the opposite team's base.
If you think you're familiar enough with the game and just want some insightful Conquest tips, check out The Overarching Conquest Guide by Branmuffin17
It's also probably not designed to be read in one sitting. I'll try to cover all basic gameplay mechanics and game modes Smite has, not just Conquest. It's a collection of information about general features of the game. Welcome! This guide is mostly addressed to completely new and freshly returning players.