Oï, and welcome to the game, dear friends !
First of all, congratulations in acquiring a frigate class ship able to mount more powerful weapons than your basic Corvette. You just discovered one of your main weapon system of your race. Here, I see you are in an Amarr station, so I will assume you are an amarr character. That nation are good users in a turret weapon system : the energy turret, which always deal ElectroMagnetic (from here, EM) and Thermal Damage, consume Capacitor for each shot, and can switch instantly between the ammo : the crystal.
First of all, the weapons in EVE Online follow a simple line : the longer the range, the lower the damage, and it work in the other way. Energy Turrets (often called “lasers”, because it’s what’s they are) come into two “categories” : Beam, which have long range and low DPS, and Pulse, which have short range and high DPS.
Second of all : as you saw, the ammo for that weapon system is the Frequency Crystal, which come in eight kinds for T1 crystals, each having flaws and forces. They come in four sizes : Small (for frigate and destroyer weapons), Medium (for cruiser and battlecruiser weapons), Large (for battleships weapons) and X-Large (for capital class weapons). You cannot use the wrong sized ammo. The total damage you will see here is for small weapon. The number is two times greater for medium, four times greater for large and eight times greater for capital. Here they are :
Multifrequency : -50% to your optimal range (the distance in which your turret will do the maximum of it’s damage potential), give no bonus to capacitor consumed per shot, but have the highest base damage for the shortest range. 12 total damage.
Gamma : -37.5% to optimal range, -15% to cap use per shot (read : using this ammo cost fifteen percent less capacitor when you open fire). 11 total damage.
X-Ray : -25% to optimal range, -25% cap use per shot. 10 total damage.
Ultraviolet : -12.25% to optimal range, -35% cap use per shot. 9 total damage.
Standard : No modification to optimal range, -45% cap use per shot. 8 total damage.
Infrared : +20% to optimal range, -35% cap use per shot. 7 total damage.
Microwave : +40% to optimal range, -25% cap use per shot. 6 total damage. Can also cook your steak.
Radio : +60% to optimal range, -15% cap use per shot. 5 total damage.
Something I didn’t mentionned before : Tech 1 crystal does not decay. Technically, you can just buy one crystal, and use it till you leave the game (as long as it is not destroyed in battle, nor do you switch weapon size). All those crystals have an “Imperial” version, which do slightly more damage, but cost more and decay (they have a limited number of shots before they are destroyed). If I remember well, it’s 8000 shots per Imperial Crystal.
When you’ll have enough skills, you will be able to use T2 energy turrets, which does more basic damage, but have access to the advanced crystals. They come by two for each energy turret type (two for Pulse, two for Beam). They are :
T2 Pulse Laser Crystal :
Scorch : +40% to optimal range, -75% to weapon tracking (Weapon tracking is how fast your turrets can turn. If it’s to low, they will have trouble to hit fast and small targets, like frigates). No cap bonus. Total damage 11. Basically, Scorch crystals allows Pulse lasers to play like beam lasers.
Conflagration : -75% to optimal range, -30% to weapon tracking, +25% to cap use. Conflagration is generally less used than the Imperial Multifrequency, because the drawbacks are generally not enough to justify the 15 total damage. It transform your pulse lasers in shotguns which can’t it small weapons.
T2 Beam Laser Crystal :
Aurora : +80% to optimal range, -75% to weapon tracking, 8 total damage. Good when you really want to snipe at extreme range for your ship size, but with low damage.
Gleam : -75% to optimal range, +25% to weapon tracking, 14 total damage. Basically it allow your beam laser to play like a pulse one.
Here, it’s quite long and I saw the others already answered, but with that you’ll have your basics in energy turret ^^
If you want to learn more, use this : Eve Univeristy : Turrets. Basically, EVE Uni is a good site where you can learn a lot on the game, even if some informations are outdated. The link I gave you will also inform you on the others weapons systems, so it’s good reading 
Fly safe !
Sasha Viderzei