An enemy can learn your Alliance Name, your Castle Name, and your Might simply by lingering the mouse over your Castle's tile on the map.
Most attackers begin by sending in Scouts without sending any other troops. Only your Scouts fight against the attacker's Scouts. If the attacker's scouts are defeated, they will not learn anything about your other defenses.
Build strong Walls to give your Troops a safe place to set up defenses. Click on your Walls to see what you need to make each kind of defense. Build Baracks and click on your Barracks to see Troops you can Train. Do Research at your Alchemy Lab to learn how to throw out Caltrops and Traps that will slow down attackers, giving your defenders more rounds to attack. In middle game, you will want Wall Mounted Crossbows to ravage your attackers while they waste rounds clearing out barriers like your Spiked Barriers. Train ranged troops like Archers early in the game to shoot at attackers during those rounds.
If the enemy units reach the wall, they will breach the wall. If their units defeat all of your units, they will take away as much loot as they can carry.
You can hide your units in Sanctuary by choosing that option in your castle. New players are advised to do so until your Might is at least 50,000. If you choose this option, the attacker will still have to fight the wall defenses, but will automatically win the fight if he gets to the wall. He will get your resources, but your troops will be safe.
Don't be terrified of battles. This is a war game. If a bully is constantly attacking you, get allies or join an alliance to get revenge.