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On the exterior of your ship, there are various "hardpoints". A utility hardpoint (aka "class zero") can only hold various utilities (special scanners, special defenses, heat sink launchers, etc).
All hardpoints that can activate (like the special scanners), can be assigned to a firing trigger, just like a weapon. Some (heat sink, chaff, electronic countermeasure) can also be assigned to a special key binding separate from your weapon fire buttons. A few (shield booster, point defence turret) work entirely automatically.
There are also a very few things (frame shift drive interdictor, shield cell bank, limpets) that are internal components and require binding to a trigger to use.
In addition to a primary and secondary fire button, you can have multiple fire groups and rotate between them.
In whatever fire group you are currently in, the items assigned to your primary trigger are listed on the outside of the right ")" in your HUD, and the secondary trigger are on the outside of the left "(". This also shows a bit of info about the items (ammo, how far along scan is, etc).
In a typical basic starter ship, you'll probably assign both lasers to the primary fire button and your kill warrant scanner to the secondary fire button. Even some very large ships may choose to equip all hardpoints in a way that allows them to assign all weapons to a single primary fire trigger.
In a more complicated weapons setup (a mix of lasers, multicannons, missiles, plasma, railguns, etc), you will set up multiple fire groups.
When bounty hunting, I would typically set one fire group as the "peaceful" one with either just the kill warrant scanner, or with an FSD Interdictor and scanner, then I would set the second fire group as either my only attack setup (lasers on one trigger, multicannons on second button) or primary attack setup. A third and fourth firing group could be used for more specialized weapons or a carefully managed shield cell bank setup.
There's an option in the bindings setup for whether or not firing auto-deploys the hardpoints. Personally, I prefer to keep that off and always bind something (like U) to explicitly deploy hardpoints.
To change your fire groups, look in the "fire groups" tab of the right panel in your cockpit.
Every time you buy or sell equipment that might need to "fire" (weapon, scanner, defensive measure, limpet controller, shield cell bank, etc etc) you should check over your fire group setup.
