In War Thunder Air Battles can be surprisingly complex. For both Air Realistic (RB) and Air Arcade (AB) you have a variety of targets to attack even as a Fighter aircraft, and many more as a Strike or Bomber aircraft.
The bread and butter of any battle will be enemy player-controlled planes. On Air AB players can field multiple planes in one battle, and each one shot down will reduce the enemy team's total score. On Air RB each player can only fly ONE plane, so if it is destroyed they cannot participate in the battle anymore. In RB it is common to win a battle by killing all of the enemy players, whereas in AB it is more practical to win by destroying other targets. This isn't a guarantee that the battle can only be won in the respective patterns, just more of a tendency.
Now, as a bomber, your targets will most likely not be enemy planes. You'll be targeting bases! Most game battles have four enemy bases to destroy. Not all game modes will have bases to bomb. If all four of these are destroyed the enemy's score ticks down to zero almost instantly. Each individual base destroyed also takes a large chunk out of the enemy team's score. To be explicit, you'll be targeting the sites marked with this symbol:
This icon hovers over a Base, which starts at full health, and the target-shaped health bar diminishes as it takes damage. As a bomber, this is your main target and should be prioritized above other targets.
If a base cannot be targeted, for whatever reason, you can target AI-controlled ground targets. This can be pillboxes, tanks, armored cars, or boats (to name a few). Destroying these will lower the enemy team's overall score too - just not as much destroying a base would. Consider these as targets of opportunity. They're usually targets for Strike Aircraft; while bombers can hit ground targets it's a bit of a waste of their total potential.
Lastly, there is the target of an airfield. In some game modes this target becomes available only if all four bases are destroyed. In other game modes, like Enduring Confrontation (Air Simulator Battles) airfields are always accessible as a bomb target. Either way, if an airfield is available to bomb it should be considered an appealing albeit dangerous bombing target. Expect to find both player-controlled aircraft and AI-controlled anti-aircraft guns nearby. Bomb it for an immense boost to your personal score and to critically damage an enemy team's overall score.
In the Enduring Confrontation mode airfields can be destroyed without actually ending the battle. They'll respawn after a short period of inactivity. In this game mode airfields have modules that can individually be bombed and destroyed for a moderate damage bonus to the overall airfield.
While it may seem obvious, it is important to note not all bombs deal the same damage. Bigger bombs will deal more damage to whatever they strike. Refer to this wikia page for a comprehensive guide to what size bomb can be used to destroy what target.
