They are diverse. In our current and past aviation inventory we've had planes that fulfill different roles. Some are dedicated to one job and some can do several different jobs. Heres some modern examples.
F-16 Fighting Falcon- small, agile fighter that can fulfill several different battlefield roles. Its pilots joke that its not 'air to air' or 'air to ground', but more like 'air to everything'. Its small size and maneuverability make it ideal for dogfighting in air to air combat, but it has advanced laser designation systems that allow it to carry a large variety of smart bombs, laser and TV guided missiles and other ground attack ordnance. However because of its small size it would be classified in this role as a 'light attack/strike' aircraft.
F-22 Raptor - Designed from the ground up for air to air combat. It carries the top of the line avionics, radar and target identification and designation systems. Im sure most of its components are classified, but you can google and find out more im sure.
A-6 Intruder - Used in the vietnam war, it was purely a light ground attack aircraft primarily used in low level strikes at night. It could not carry air to air missiles and did not have a gun, thus making air to air engagement impossible.
B-2 Bomber - A stealth aircraft. Would be classified as a strategic bomber, or a heavy strike aircraft if you wanna call it that. Designed to drop heavy ordnance, either conventional or nuclear, on strategic targets deep behind enemy lines.
There are tons of others i can think of, The F-4 Phantom, the F-14 Tomcat, the F-15 Eagle, the AV-8 Harrier, and dozens of others that can fulfill several different roles, from low level ground attack to high altitude air to air interceptors. Bottom line is we have aircraft that are built to do one specific role and do it very well, and we also have aircraft that are more jack of all trades that can fill several different battlefield roles.
Hope this helps answer your question!