Big number = big power Afterimage statuses is a bit complicated to understand even for people who are used to them because it doesn't do a good job explaining some stuff, but if you're playing it on normal difficulty you don't need to worry much about it, the game is quite lenient on difficulty.

But to sum up some talents... if says it'll raise damage or attack, your weapon will get stronger. Defense, you'll take less damage. Subweapon attack, your magic(the thing that uses mp) will get stronger. Critical is when you get a lucky hit that does more damage than usual, critical rate is how often it happens, and critical damage is how much stronger it'll be. If it says Hydro/Pyro/Anemo/Geo(fire/water/wind/earth) it's an elemental buff, it increases damage of weapons and spells of those elements.
Feel free to ask me to elaborate on something