You're on the right track for the early uses of airplanes in WWI. Originally, planes were used for reconnaissance and played a critical role in the ability of the French and BEF to react to German advances. When opposing planes would find each other in the skies they began taking pot shots at the opposition with pistols and shotguns. Their success rate was incredibly low.

Both sides recognized the value of aerial reconnaissance, and soon there were dedicated planes to try to deny the opponent the ability to photograph their movements. The Fokker Eindecker and Morane Bullet were early monoplanes that featured a single machine gun that fired through the propeller arc. The Bullet simply armored the propeller and dealt with the inevitable ricochets. The Eindecker used a new invention that would be featured on nearly all future WWI fighters--the interrupter gear. This mechanism suspended the firing of the machine gun when the bullets would hit the propeller, allowing for a safe way for the pilot to simply aim his entire plane at the enemy and try to shoot it down. Planes rapidly shifted to biplane designs and the technological edge shifted back and forth a number of times. The goal was to secure your own ability to do reconnaissance and deny it to the enemy. The targets were enemy recon planes, observation balloons, and the fighters that protected them.

Later in the war, dedicated bombers would appear. Single engine ground support aircraft were produced, but they were quite vulnerable to ground fire given the small amount of armor they could take aloft. By WWII ground support aircraft would be able to have a good chance of surviving attacks on ground troops due to their more powerful engines allowing heavier armor over vital equipment and the pilot, but WWI ground support aircraft were too fragile for the job.

Earlier in the war, the (in)famous Zeppelins were used for strategic bombing by the Germans. Later in the war, planes like the Gotha bomber were used for this purpose. They were unable to carry the huge bomb loads of WWII bombers, but they were huge for their day and quite capable and caused hundreds of deaths. These efforts were mirrored by Allied bombers like the Handley-Page O/400 which were quite similar to the Gotha in many respects. Daylight bombing was generally found to be unsustainable due to losses to fighters and antiaircraft fire, and night bombing attacks were attempted. These bombers inspired interwar bomber theorists like Douhet in Italy, Mitchell in the US, and Trenchard in the UK. You can draw a straight line from WWI strategic bombers to the interwar theorists to the huge bombing raids in WWII.

To a smaller extent, there were naval aircraft employed in roles from scouts to antisubmarine warfare to signal planes. The full development of the aircraft carrier mainly came about after WWI.

I hope that answers your question. Followup questions from OP and others are always encouraged!